# What are the most common mistakes that beginners of (La)TeX and Friends make?

I want to collect the most common mistakes, misconceptions, pitfalls, etc that (La)TeX and Friends users make. Please one answer for each mistake, misconception, pitfall, etc.

I am only interested in more technical, objective cases rather than psychological, social, subjective cases.

From this complete infinite list of technical and objective cases, we can have a reference how to teach newbies much better directly or indirectly via writing a good book.

The technical and object cases are, for example, as follows.

• Beginners sometimes use $\huge E=mc^2$ with the hope they will get a huge formula. It actually does not produce the expected result. The correct way is \huge $E=mc^2$.
• Beginner sometimes use longtable inside table because they assume longtable is the longer version of tabular which is able to be sandwiched in table.
• etc.
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Not reading an introduction and package documentation. –  Marc van Dongen Oct 21 '13 at 11:36
Aside from answering questions on this site when I don't have a clue what I'm talking about? –  Jubobs Oct 21 '13 at 12:25
There is a similar Community poll on meta: meta.tex.stackexchange.com/a/1596/2693 –  Alan Munn Oct 21 '13 at 13:21
I don't really see how this can get sensible answers, I voted to close as "too broad". As @AlanMunn says the question on meta is perhaps a more suitable location (although it is not really a meta question about the site either) –  David Carlisle Oct 21 '13 at 13:53
Isn't this a sort of "everyone rant here" question? –  marczellm Oct 22 '13 at 21:28

Another common mistake made by LaTeX newbies is to think that the \title command typesets the title and forget to use \maketitle to do that.

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Judging by questions on this site - which I admit are probably not representative of beginners as a whole but which are, at the very least, of special interest to readers likely to peruse this answer - I would say that one basic mistake, which leads to a number of others, is not stepping back and getting a general sense of the capabilities of TeX & friends. I don't mean the details, but the 'big picture'. For example,

• TeX & friends are good tools for typesetting text, mathematics and bibliographies;
• TeX & friends are great for automatically ensuring consistent layout, accurate references and cross-references;
• TeX & friends are not the best tools to create a database, manage a spreadsheet or draw elaborate 3D scenes with accurate perspective and lighting;
• TeX & friends are not good replacements for tools such as sed, (g)awk and grep, although many editors provide much of their functionality;
• neither TeX nor friends are good replacements for a sheepdog;
• TeX & friends make at best indifferent tea.

In particular, TeX & friends are much better than human beings - and much better than many other programmes - at the things they do well. They are not generally good - and typically much poorer than alternative programmes - at the things they are not intended to do.

One key strategy for getting the most out of TeX & friends is to use the right tool for the right job. Some questions boil down to requests for TeX solutions to the problem of brewing the perfect cuppa. This is a perfectly reasonable aim but the best answer involves advising a non-TeX solution.

Other questions essentially ask for TeX-based cat-herding solutions. The best answer in this case involves recommending against adopting the goal set out in the question.

However, these types of answers are rarely appreciated and frequently interpreted as either lacking in imagination ('I don't believe it is not possible/advisable') or as admissions of TeX's failure to rise to the needs of twenty-first century users ('Super Programme can make tea while simultaneously sheering sheep, sending a letter to my gran and paying the gas bill'). This is a shame since these really are the best answers in these cases and appreciating TeX's limitations, as well as its strengths, is key to using it effectively.

[That is, I am extremely sceptical of solutions of this kind.]

Cup of tea is from openclipart.org.

'Like Juggling While Herding Cats' is by Robin Catesby and available here under this CC licence.

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Trying to convince people that LateX is the best "program" to make your things done in a stylish way. Resulting in two possible reactions... 1) being called, mailed or texted a lot (and I mean a lot) about "how can I do this, how can I do that, is it possible to ... (so I send them to this site.) 2) I can do the same things in WORD... :-(

I don't know which one is the worst...

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The newbies don't use enough packages to get their work done. The best example is %, the siunitx package provides sophisticated way to print percentages but new users don't use it.

Another major mistake which they do is, they don't use updated distributions of TeXLive or MikTeX or update the packages atleast.

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Forgetting to add fontenc package when using accent letters.

\usepackage[T1]{fontenc}

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My own take on this question is more about the mistakes beginners make because of us. I made too many shameful mistakes (and still do at times), but with my first private beta, I realised that many beginner mistakes were in fact my beginner LaTeX developer mistakes.

They are still beginner mistakes – but I have a feeling of responsibility for a lot of them.

1. Not teaching users to first read the documentation. Not teaching users to look at the code if the documentation is unhelpful (code does not bite). I have had someone tell me "I didn't dare to modify your package because I didn't know what I was doing"… well, just back it up somewhere and play, code is not sacred).
2. Not teaching users to send you the log when they want to report a bug or any other issue, even if they do not understand what the error message means. On that matter, I feel like it is helpful to teach all beginners how to read the most basic errors (command already defined, command not defined, underfull and overfull boxes).
3. Not writing appropriate documentation files for users (we all boast about "literate programming" and we mostly do a good job at writing docs, but not all of them are perfect). We have some beautiful files, and also some barely-commented "implementation" docs with just an introduction and a list of macros that no beginner would ever understand.
4. Not teaching users the difference between form and content (as mentioned several times before). But I also mean it literally: whether they want to code something for themselves or whether they are requesting a new feature, they need to determine if it is just a stylistic preference or if there is a general purpose behind it (e.g. do we need a simple command or an option for customisation). There is nothing more stupid than creating a whole system that works really well except it is totally impractical in real life.

I hope it is not off-topic… but thinking back, I would think that most of my own beginner mistakes were also often developer (or documentation-writer) mistakes. We are generally good at writing documentations, but we sometimes have a hard time finding the right words for both beginners and experts.

Most of the beginner mistakes mentioned here are not really in the books… or at least they don't show up as sections, tutorials, etc. It is no wonder beginners first look things up on google. We don't write documentations on debugging what we assume will work (it works in the hands of a TeXnician, not in the hands of someone who does things at random).

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+1 for mention that makes a difference the documentation written for human beings, err ...average users. Sometimes, each option of each command is explained extensively, but you have to search in Google for an example or how apply these commands without obtain errors. Generally, the average user needs the section "usage" and some examples, not the "implementation" section. Instead, sometimes even is omitted that one must have \usepackage {...} in the preamble. Too obvious? not for a novice! –  Fran Jul 30 '14 at 8:56

Not using version management for your document.

I've introduced some colleagues to LaTeX, and the most common questions I get relate to how suddenly something doesn't compile and how it can be fixed yet, when I ask them about reverting to a previous version, they consequently say they never thought of putting their work into a version management system (funny enough they manage all their other CompSys code related tasks in it). I now mention this even to beginners as one of the major benefits of working in plain text.

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This is so true! But I'd say it's even more of a trouble with Word documents. I have seen people having thesis directories containing files like: thesis-draft-n-date-hour.doc(and Word documents are generally much bigger than LaTeX source code, that's simple plaintext, hence having 100MB of directory wouldn't be so strange for a long thesis.) –  Bakuriu Oct 24 '13 at 11:40

Several days ago I taught my students how to plot some functions that are either algebraic or transcendental. As usual I introduced them to PSTricks for the sake of its full support for PostScript language.

All functions are expressed in infix form. Some of my students got confused with the algebraic key. They assumed that this key must be enabled via algebraic=true whenever they plot algebraic functions and set it to false whenever they plot transcendental functions. The code they wrote is more and less as follows.

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-plot}
\def\AlgeFunc{x^2-4} % an example of algebraic function
\def\TransFunc{sin(x)} % an example of transcendental function

\begin{document}
\begin{pspicture}(-3,-5)(3,2)
\psplot[algebraic=true]{-2}{2}{\AlgeFunc}
\psplot[algebraic=false]{-2}{2}{\TransFunc}
\end{pspicture}
\end{document}


Actually the algebraic key was created by PSTricks maintainers to allow users to switch from postfix expression (the default in PSTricks) to the infix one or vice versa by setting this key to either false (default) or true.

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I'm a little late to that party, but ho—that's good… –  Sean Allred Jun 19 '14 at 12:14

Using floating environments (table and figure) in beamer.

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1. Compiling too early and too often. Now you are spending your time working on fixing formatting and such that will change as soon as you add more text anyway and all the floats will move anyway.

2. Using floats when you don't have to. Floats are the devil, yet all tutorials use them. Most of the time I know where I want the image, at least roughly, and didn't know for ages that I could just insert the image without wrapping it in a float, so I'd spend ages trying to get stuff to stop floating down multiple pages, or into the wrong section, etc.

Edit: As this is attracting a lot of debate: When I started every example shows you to insert an image in a float, so I thought you had to use float. Even a couple of months ago I thought you needed to put a table in a table environment; I'd still have to look up how to make a non-floating table. This is a problem as a lot of the time I need an image in a certain place. For example, if I'm typesetting a homework problem (Something I did a lot as an undergrad, and am now doing again when I'm writing questions) I can't have that image floating down into a different question; my TA or prof isn't going to go hunting for it, they are just going to dock me marks (And I don't want to confusing anyone working on my problem set!). Also as the h option is a joke they usually float far away. I don't mind if a figure floats a few paragraphs, but three pages away is bad: Same page as the discussion or facing page only. I should always be able to see both figure and text at the same time, unless there are exceptional circumstances or a very large text (I cut some slack when writing my thesis, as there were so many figures they wouldn't all fit on the same page as the text).

There are times floats are the right choice; I'm using one in the document I'm working on right now. However, they are just as often the wrong choice, and a lot of new users don't realize this.

3. Using outdated packages that some website gave you My group drives me crazy since they use very outdated packages that have been superseeded. subfigure instead of subfig, stuff like that.

4. Relying on GUI text editors instead of understanding what is happening People at work also drive me crazy with refusing to use anything but the compile button in WinEdt. If that doesn't automatically work, they refuse to use the package (Thus no biber, no biblatex, etc.

5. Using MikTeX That install package on compile thing NEVER works right. Hard drives are large, dammit.

Edit: Ok, not never. But it fails every time I've given my coworkers a new package to use, causing us to have to go into the interface and have it manually install.

6. Limiting yourself to what chemistry journals allow for everything I dream of one day being editor of a big chemistry journal, just so I can go to the AMS or APS and borrow their code. This has things like not using macros, not redefining things, not using excess packages (or in one case, not using packages AT ALL).

7. Not being willing to put in time understanding LaTeX The people I work with just want a solution now. They aren't willing to put in any time into making it work; they want something that works now, since the journal will reformat it anyway, so if it works and gets vaguely close to what they want, good enough.

8. Making DocumentNameV3.tex and forgetting to open the new PDF, then wondering why nothing you do is working Not that I've done this recently, after I was too lazy to set up a new code repository.

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Major complaint from colleagues I've heard is 7. –  Forkrul Assail Oct 23 '13 at 19:58
I disagree (partly) with 2: I think floats are a good thing: often images and tables don't need to be looked at immediately and the readers should have a choice when they do. So it's a good thing if they float to the top or bottom or a separate page. They have a caption and are referred to in the text anyway –  clemens Oct 23 '13 at 20:00
Floats are great when they're appropriate, but using them when you want your text to stay put is a mistake. Too many people use them but don't want them to ever float. Double mistake. –  alexis Oct 23 '13 at 20:03
@cgnieder I think what Canageek has in mind are people using figure when all they want to do is insert a graphic. There are many places where this is useful, and new users simply do not understand the difference. Quoting myself from chat: "The prize for the worst name choice in LaTeX surely must go to the figure and table environments. I wonder how many questions here and on the web deal with people not understanding the difference between the container and its contents?" –  Alan Munn Oct 23 '13 at 20:06
@Canageek do you know \FloatBarrier (from the placeins package)? I never used it but it's designed for exactly that purpose... –  clemens Oct 24 '13 at 21:01

Attempting to use \ifeven...\else...\fi that actually does not exist. Note that only \ifodd...\else...\fi is available. Probably Knuth likes odd things.

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Is this really a beginner's mistake? It took me quite a while to get to the point of using conditionals and, even then, I was using the ifthen package rather than TeX-like \if and friends! Until I read your answer, I'd never even heard of \ifodd. –  cfr Sep 21 '14 at 18:32

Not making enough use -- or (sadly all too frequently) not making hardly any use -- of the opportunities afforded by LaTeX to separate the content of a document from its visual appearance. In particular, too many attempts to engage in visual formatting at early to intermediate stages of writing a working paper, a technical note, or whatever.

Addendum: The answer by @Alexis gives quite a few examples of mistakes that arise when one engages in (too much) visual formatting...

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Good man Mico. I was the first to plus one you yesterday. Using LaTeX only works if you forget about the visual appearance or if you're a guru. In both cases you need the structure offered by LaTeX. –  Marc van Dongen Oct 22 '13 at 10:00
@MarcvanDongen - Wow, thanks for the compliment!! –  Mico Oct 22 '13 at 11:32

Often beginners are not aware of the different whitespace and possible linebreaks:

## Cancelling an "end of sentence" space

A space right after a period following a lowercase letter by default ends a sentence and LaTeX inserts an extra whitespace. There are several occasions where you do not want to have the default behaviour. For example,

Ms. Bean is \ldots\\
Ms.\ Bean is \ldots


To make the Ms.\ Bean unbreakable, use ~ instead of \<space>. \<space> and a ~ differ only in their line-breaking behaviour, the whitespace is the same. See also: When should I use non-breaking space?.

## Enforcing an "end of sentence" space

A space right after a period following an uppercase letter by default represents an acronym and LaTeX does not insert an extra whitespace. There are several occasions where you do not want to have the default behaviour. For example,

I left at 12:00 P.M. In \ldots\\
I left at 12:00 P.M\@. In \ldots


produces

## Enforcing a space after a control word

Control words eat spaces that follow.

\LaTeX is fun.\\
\LaTeX\ is fun.


The \<space> here is necessary to produce space between LaTeX and "is". An alternative is to use braces to terminate the command. For example, \LaTeX{} is fun. and {\LaTeX} is fun. are equivalent to the above. See also Spaces after Commands.

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@Marienplatz Intra, not inter. As in, I moved from Dr.~Leznoff to Dr.\ Leznoff. –  Canageek Nov 2 '13 at 21:20

DONT Read tutorials that advise best practices from the stone age.

Especially german LaTeX tutorials advise something like this in the preamble:

\usepackage[latin9]{inputenc}
\usepackage[T1]{fontenc}


Then i see a lot of people that are writing umlauts like this: \"u. Please forget this!

DO In times of UTF8 use \usepackage[utf8]{inputenc} and you're done. No need for magic to write foreign characters!

DO Another good advise is to use xelatex instead of pdflatex to compile your document. The advantage is, that you can change the fonts in your document quite easily, without shooting yourself in the foot!

DO Read and try to understand the build log! Looking for the source of compile errors is quite hard for TeX beginners (sometimes even for more advanced users), thus it's very helpful to get a look for relevant error messages!

UPDATE

DO Use the nag package (\usepackage[l2tabu]{nag}) to get warnings when using bad practices or obsolete TeX-style commands. It is also helpful to read the documentation ( german "Sündenregister", english). After reading this, you can decide if a tutorial is using obsolete commands or other bad practices.

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»DONT Read tutorials that advise best practices from the stone age.« -- that's easily said but how should a newbie judge if a recommendation is outdated? –  clemens Oct 22 '13 at 8:59
@gerrit it's unnecessarily complex. To much complexity is always bad ;) –  klingt.net Oct 22 '13 at 10:24
This is the most important post up until now, in my opinion. Way too many tutorials on the internet are outdated, and people learn only stoneage-style LaTeX! As an example, 99% of the tutorials still recommend BibTeX, although BibLaTeX and biber are now very stable, and absolutely ready to use. –  Ingo Oct 23 '13 at 10:17
I disagree on \"u and such. I don't have such symbols on my keyboard and it is a lot easier for me to type an accent that way instead of googling the character to find a copy I can copy and paste into my document. I use utf8, but don't WRITE it like that, I just want it there in case I do copy that character in. –  Canageek Oct 23 '13 at 19:24
@Canageek You may want to check out the US international layout (with AltGr and dead keys). With minimal transitional pain I write German, English, Swedish and the odd French word without switching anything. And, of course, all the programming symbols are where you need them. –  Raphael Nov 3 '13 at 1:57

The most common mistake that LaTeX beginners make is that they start with the “stock” article class and enrich it with various packages to suit their needs, instead of picking a more specialised class providing all the functionality they need.

It has several drawbacks for the users:

• They spend a significant time trying looking for “tabular package XY” that can do “plop plop fizz fizz” instead of using what is provided by the specialised class they did not pick.

• They spend a significant time trying to make some packages work together and looking for answers to their problem.

• They spend a significant time trying to customise the class to achieve a pleasant layout, while they wether have the needed programming skills neither (most probably) the design skills.

Is there any LaTeX introduction or tutorial that emphasises the choice of a document class and provides useful resources (catalogue, comparison of features, application domain) to choose one? It seems to me, most of them pick one (article) and stick to it for the whole tutorial, while it could be more useful—once the basics of text and math typesettings have been covered—to drop that generic class in favour of a specialised one.

To put it in one sentance: “unexperienced users confuse the roles of designer and scripter (and tutorials tend to perpetuate this confusion).”

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I have never used anything BUT article. What else is there? KOMA-script and memoir seem to be languages in themselves, and half my packages warn that they are incompatible with one or both! –  Canageek Oct 24 '13 at 21:01
This answer would be much more useful with some real examples, i.e. packages that are often used but aren't needed when using a specific document class(either because it provides the same output or because the document class can do the thing slightly differently, but in a "better way" from the typesetting point of view). –  Bakuriu Oct 25 '13 at 9:41

## I will hammer home my case for books! This is LaTeX!

Besides not using Emacs, I guess 90% of newcomers don't buy books, but try to learn "LaTeX by Google". What a waste of time.

Edit: OK, borrow books, also possible. Somebody else with such proposals? Maybe I'd betters say that studying a book as a beginner seems the crucial thing.

»Works pretty well«: Sure, but it takes much more time than take the book from the shelf and read. How many users never heard of »texdoc packagename«? And I'm quite convinced that "LaTeX by Google" works for nerds (but it surely costs much more time), but if you are studying the humanities, a book explaining the concept is really helpfull.

Edit 2: »Books are sooo last millenium«: Yess, and probably 99% of the users here as well. Besides that, courtesy of F. Mittelbach we present: The companion as ebook!

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Worked pretty well for me. Just saying. –  Sean Allred Oct 21 '13 at 12:31
Books are so last millennium ;) I don't recommend books for learning any programming-like method anymore. What is needed, however, is a good approach to learn-by-Google; it's not enough to simply snag the first half-working snippet and bend it to your needs. You need to be hunting out the reasons behind the code. –  Jack Aidley Oct 21 '13 at 13:39
Googling latex <package name> is by far the quickest way to get to the package's original documentation on CTAN. And once you have it, you can do a full-text search. On the other hand, I've yet to see an online introduction to LaTeX that comes close to the introductory books on sale. Books are best for educating yourself, PDFs for looking up tidbits. –  alexis Oct 21 '13 at 15:31
@alexis texdoc <package name> on the command line works pretty good as well :) Also texdoc latex2e, texdoc lshort, ... –  clemens Oct 21 '13 at 16:44
@alexis try that with color :). I would generally rather recommend ctan <package> this usually gets rid of chemical, fetish and other unwanted results. –  Max Oct 22 '13 at 14:22
• Not understanding the difference between typesetting and word processing. The latter is simply using computer technology to replace a mechanical typewriter, primarily in the production of routine business documents. The former has to do with preparing documents in their final form for publication. TeX and Friends are typesetters, not a word processors.
• Thinking TeX and Friends are solely for preparation of documents intended for scientific/academic journals, classroom notes or textbooks with lots of formulae and/or footnotes and citations. TeX and Friends certainly excel at these tasks but also excel at typesetting poetry and prose -- in their original form, not just in textbooks or critical analysis (although TeX and Friends do an outstanding job of preparing those as well).
• Not understanding the difference between logical markup and WYSIWYG then spending inordinate amounts of time trying to make TeX and Friends behave like a WYSIWYG desktop publisher/word processor instead of putting their focus on the content of their document.
• In a similar vein, not understanding the difference between writing a document and designing a document. Two different disciplines, two different concerns. TeX and Friends allow a clean separation of the functions even if the same person is going to do both.
• Trying to make TeX and Friends do everything instead of using the right tool. Production of a consumer-oriented magazine is far better done in Adobe InDesign than TeX and Friends. Business presentations are far better done in PowerPoint than Beamer. etcetera, etcetera etcetera.
• Underestimating the amount of work it takes to produce a "beautiful" document. TeX and Friends will produce more beautiful documents than MS Word but it is not automatic simply because one uses TeX and Friends.
• Getting caught up in vim vs emacs vs texworks vs tex{studio | maker} vs notepad arguments on SX (or elewhere). :) They all work fine. TeX and Friends don't care which you use and the resulting documents don't either.
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Compile early, compile often as with 'test early, test often' is good advice when spending a lot of time working with complex documents and multiple included files. A common mistake is to work too long on a particular section, not noticing a missing } and then having to scour multiple documents for hours, when this could've been fixed by either an automated constant compile, or just ensuring every section or paragraph you work on still leaves a coherent document.

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Compiling to make sure it compiles is a good idea (always compile before commits!) - but that's different than tweaking the output every time you compile. –  bombcar Mar 13 '14 at 15:35

Another common misbehavior is reading package or class documentations from TeX mirrors (the worst case, they read from sites with obsolete contents) even though they already installed the complete, up-to-date packages and classes.

I mean that they don't know that texdoc <package-name> invoked in their own machine can launch the documentation in question.

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Unfortunately it is not always clear what <package-name> is (like with KOMA-Script). In MiKTeX texdoc <package-name> opens a HTML list of documentation items of the given package, while texdoc --view <package-name> opens the first item of that list. In the case of Beamer this is only the logo, with PGF it's the mindmap example, with NewTX the implementation notes etc. You have to know the filename: texdoc beameruserguide, texdoc scrguien etc. –  marczellm Oct 26 '13 at 9:11

## Inconsistent syntax causes confusion

As there is a bit inconsistent syntax between length and counter, some users get confused with whether or not they need \.

They often wrongly type \setcounter{\countername}{<value>} rather than \setcounter{countername}{<value>}

and/or

\setlength{lengthname}{<dimen>} rather than \setlength{\lengthname}{<dimen>}.

Who made such an inconsistent syntax?

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The first error for many TeX newbies is not backslashing figure brackets in formulae, when it should be backslashed. So they get $\min {x, 100 - x}$ or even $min {x, 100 - x}$ instead of $\min \{\, x, 100 - x\,\}$.

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The mistake I always make, even to this day, is forgetting that newlines have syntactic meaning in LaTeX. I'm so used to using empty lines to delimit my text that I do it automatically, and then end up with ugly text (especially when indentation of the first line is enabled).

The other mistake I always make is forgetting when some command requires arguments, like \array, and then it automatically eats up the first thing after it, leading to the "why isn't it rendering the first element of my matrix?"

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Once I've seen a document template with a comment along the lines

% Tip: Always use eqnarray instead of align


:-(

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At the very beginning, trying to make a table in this way:

\begin{table}{ccc}
a & b & c \\
\end{table}

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@mafutrct To make a table in LaTeX you need the less intuitive environment tabular, not table. There is also commonly used the table environment, but is not to make a table, so the confusion is served for the novice. What a table environment does is move (float) a table (or whatever it contain) to the best possible place according to several rules (the top of the page, the bottom, the next page, etc.). –  Fran Jan 6 '14 at 9:22

Personally I think, it is not to care if a given solution is deprecated. So the nag package, as "old habits die hard" and those are too much widespread all over the web.

Last but not least, not to search tex.stackexchange.com which helped me more than a hundred times so far. It helps to distinguish high value answers from bad code snippets in some boards.

I think anything else has been said, already.

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The usage of raster graphics (JPG, PNG, ...) instead of vector graphigs (SVG, TikZ pictures, ...) could be a mistake since this increases output PDF file size and slows down rendering in several readers.

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So we have to vectorize all screenshots or photographs? I don't think they become smaller in size. –  kiss my armpit Oct 22 '13 at 12:36
sometimes it's really necessary to incorporate photographs, say for presentation of historical information, and they simply don't come in vector form. rather than disallowing them, it would be better to give a warning and offer a way to compress them in the most nearly lossless manner. –  barbara beeton Oct 22 '13 at 21:31
It's also a mistake to use JPG instead of PNG for diagrams and line art-- it makes the lines and letters fuzzy. But it's not specifically a (La)TeX mistake. –  alexis Oct 23 '13 at 19:12
@my_greets Getting SVG to work in LaTeX is a pain, and using a PDF for an image is also a pain, and conceptually wrong (it is a document layout format, NOT a graphics format!) –  Canageek Oct 23 '13 at 19:28

Actually it is not wrong but the output might make your eyes a bit itch. "Wrongly" representing a series of unaligned equations using $..$ instead of using \begin{gather*}...\end{gather*}.

\documentclass[preview,border=12pt]{standalone}
\usepackage{amsmath}
\begin{document}
\section*{Not recommended}
The solution of $x^2-5x+6=0$ is
$(x-3)(x-2)=0$
$x-3=0 \text{ or } x-2=0$
$x=3 \text{ or } x=2$

\section*{Recommended}
The solution of $x^2-5x+6=0$ is
\begin{gather*}
(x-3)(x-2)=0\\
x-3=0 \text{ or } x-2=0\\
x=3 \text{ or } x=2
\end{gather*}
\end{document}


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recommended shouldn't be recommended. In fact this shouldn't be done in my opinion. –  percusse Oct 23 '13 at 15:29
• Not realizing an empty line is a \par and trying anything and everything to work around the spacing problems. This is probably among the top five and I would patch that out if I could.
• Using inline math instead of display math and screwing up the line spacing in progress. Points for using \displaystyle in an inline math in a normal paragraph.
• Using random solutions/templates/code pieces from the internet. Yesterday I saw someone actually confused about why using

\documentstyle{foo}
\usepackage{bar}


throws an error, after he found the first line on the internet. I wish there were a way to get rid of the old pages that still show up with latex 2.09 code, yes weinelt.de you first. This goes further than @klingt.net. @Keksdose's solution is a remedy to a certain point, because the printed material is usually of better quality, but even there outdated solutions are advertised sometimes.

• Using babel without the shorthands turned off and then being surprised that it messes up math, ipv6 adresses, listings or any other random thing. This 'feature' is my personal pet peave.

Edit, now with examples: Problem with spanish babel package Conflicts with Datatool and babel (french) tikz declare function and babel french option Why does the package babel[french] destroy \@for loops? Tikz and babel error I've also seen problems with other packages in the past, listings and syntax from mdwtools come to mind immediately, but there are more.

• Accidentally redefining commands with def.

• Using incompatible packages or order sensitive packages in the wrong order. To be honest latex should make that harder or prevent that. Bonus points for obscuring the order to scrutiny by including a package multiple times.

• Including redundant packages. Recently seen preamble:

\usepackage{lmodern}
\usepackage{mathptmx}
\usepackage{ae}
\usepackage{courier}
\usepackage{mathptmx}
\usepackage{fontspec}

• Manually trying to set variables instead of using proper packages. Most common with parskip, setspace and geometry.
• Declaring one encoding and using another or mixing different encodings.
• Ignoring Italic corrections.
• Using the wrong quotes (e.g. "" instead of '').
• Floats where they make no sense at all. Today I saw someone combine a table with Absolutely, definitely, preventing page break just to get a caption and latex was not happy.
• Not using non breakable spaces, where needed Dr.~Foo
• Not knowing when to use math and when not. Also not using \text{} in math mode for non math.
• Not escaping _, #, ^ and friends.
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A colleague once asked me help because the name of his Turkish coauthor caused errors (something like Şukur); of course he had \def\c{\gamma} in his document. –  egreg Oct 22 '13 at 20:26

Doing by hands what LaTeX should handle. Like writing "on page 3" and thinking to learn "complicated things" like \label-\ref "later", i.e. never. On the other hand, it is not bad to use \newpage before \section instead of titlesec package --- this is what David Carlisle already answered about.

Basically this applies to all kind of systems. How many keyboard shortcut in Word to learn, how many packages to remember in LaTeX... It always depend on how much one is going to use some software.

Another one on meta-level: not asking computer support when you have one available. Many have used hours to find out things that I could have tell in a minute.

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Fight typesetting with tooth and nail.

Many try to emulate what they know no matter what. Examples include:

• Switch to Times New Roman. What, you can change the math font?
• Use \\ liberally to break lines and delimit paragraphs.
• Ignore the concepts of floating environments.
• $...$ is the only math environment you know; spacing with \\.
• Never use -- or ---, let alone .\ and \, in acronyms.
• All math delimiters have the same size.

Not exactly typesetting, but related in spirit:

• What are \label and \ref?
• Instead of using the ones from babel, use wrong or hacked quotes (language dependent).
• Literature references hardcoded in footnotes.
• Re-use pixel graphics created with some drawing tool.
• Write everything in one huge file.
• Use a *TeX distribution that is older than your PC.

Of course, the most common mistake is to write stuff yourself. In 95% percent of the cases, there's a package that does what you want!

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@Canageek I think that is not only a narrow definition of "document", it's also not a useful point of view. The graphics ends up in a PDF (PS + x) so they have to get there somehow. LaTeX engines may be able to hide from you that they convert SVG to PS/PDF but it still has to happen (would you rather control the conversion?). Provided you don't want pixel graphics, which would be really contrary to the "idea" of PS/PDF. (Or, you know, learn TikZ. :)) –  Raphael Nov 2 '13 at 22:36