I only partially concur with the standpoints of the other answers. It certainly is good to avoid fiddling with typographic layout too much if you don't know (yet) what you're doing. Most novice users come from a MS Word background and are used to deal with typesetting differently, so in order to get to (good) terms with LaTeX, one should try to accept the settings of the basic classes in the beginning.
But many users get to LaTeX for a thesis of some kind, which often have strict requirements regarding the formatting. While these requirements tend to be typographically ... suboptimal, they are a reality that needs to be dealt with. Hence, adaptions need to be made. Given this, it often seems advisable to use a package instead of manually fiddling with settings. A well-known example of this is line spacing: It's better to use the package
setspace instead of changing
\linespread. I think the same applies to paragraph spacing, if needed: It's better to use the package
parskip instead of manually changing
Furthermore, there are some packages that are essential for any non-English document (
babel), that no user should feel obliged to restrain from using. Other packages improving the layout can pretty safely be loaded and don't do harm (
booktabs), so there's no need to stay away from these. While I don't usually typeset math in LaTeX, I think there's a bunch of packages that you need for relatively basic math (i.e. the AMS math packages).
So here's some advice for new users, coming from me as a relatively new LaTeX user (1.5 years), who doesn't have a lot of TeX knowledge as a background, but is deeply in love with LaTeX:
- Find out about some underlying principles of LaTeX, how it's different from ordinary word processing software, and how you can use these differences to your advantage. I highly recommend reading The Not So Short Introduction to LaTeX2e all the way through, only skipping sections truly irrelevant for you (languages you don't use, perhaps -- like in my case -- math and drawing).
- Don't change the basic layout if you don't need to.
- Only use a package if you know why. Try to find out what packages are good for your desired output. You'll find popular solution-packages to common situations at What packages do people load by default in LaTeX?.
- Develop a template with packages you need and which are useful. Always make comments (
%) why you're using each package. If you feel they're not necessary after using the template for some months, you can still remove them.
- Read the other answers to this question as they present a slightly different take on this matter and some good advice