LaTeX

LaTeX is a typesetting system. It is used almost exclusively in the scientific and math communities for typesetting papers.

Web Resources

Wikibooks: LaTeX - great general resource explaining LaTeX in plain English; this page is also an excellent resource for finding specific commands (e.g., text sizes)
The Comprehensive LaTeX Symbol List - massive PDF document containing 3,000+ symbols that can be used in LaTeX. Perfect for math/theoretical papers.
Google - despite being obvious, searching for terms like latex binomial coefficient generally works well if you're unsure how to typeset something.

Use Wikipedia. A lot of math articles (e.g., Binomial coefficient) have images autogenerated from LaTeX input. Clicking the edit this page tab at the top of an article will reveal the source that you can learn from.
Don't focus on formatting. This is where LaTeX is supposed to do its magic. If you're spending a long time introducing hacks into your document to make it appear a certain way, you're probably doing it wrong. Look around on Wikibooks or Google for a better way.