I am writing a lot of documents mostly with mathematics in them.
I personally leave 1cm space between sections/subsections etc and the text below them and a 0.7cm space between text and math formulae. Also an 0.3cm space between paragraphs. I have adjusted these values only because I like the output.
There are a lot more customizations that I use for example I always use
\displaystyle (although there are a lot of you that have warned me against it and I believe that there is a good reason for it, but I really like it), also I don't want to mix text and math so I generally place math in a new line (with a space of 0.7cm as I said).
Sometimes I make up my mind and I change the spaces I use or some of the other customizations...
So I would like to ask all of you writing documents (books included) is there any special way or special rules that someone must follow for the size of the formulae or the spaces or generally for the output? Are you following any guidelines? When someone is being given a manuscript to typeset does he do whatever he likes based on the output or is he following some rules?
For instanse when I want to write different sentences I leave a space of 0.3cm as you can see: