LaTeX and mathematics go well together.
At the risk of preaching to the converted, this post sets out
(a) reasons to learn to write mathematics in LaTeX,
(b) a few free internet guides on learning to write mathematics in LaTeX,
(c) several internet resources which can facilitate writing mathematics
in LaTeX.
Reasons to Learn to Write Mathematics in LaTeX
There are many good reasons to learn how to write mathematics in LaTeX.
 LaTeX encourages mathematical writing.
It's just plain text.
It's easy to write, copy, and paste formulas.
That which is easy gets done.
 Many websites such as Wikipedia, Stackexchange, Wordpress blogs, and so on use LaTeX to render mathematics.
Thus, learning mathematics and LaTeX pays dividends
in many places.
 LaTeX demystifies the complexity of mathematical texts.
Before learning LaTeX, my mind boggled at the apparent complexity of mathematical documents. All the numbering, crossreferences, and symbols that appeared so complex, appear relatively straightforward from the perspective of LaTeX.
 LaTeX fosters skills in verbalising mathematics.
The markup is similar to verbalised mathematics.
Along with
pronunciation guides
and
mathematical video courses, writing LaTeX
can be particularly useful
for the selftaught social scientist.
Getting Started
If you're completely new to LaTeX, check out
this guide by David R. Wilkins.
In regards to getting started with writing mathematics in LaTeX,
the internet is filled with resources.
The following are two goods guides:
Setting up a Learning Environment
The following links provide an environment of
rapid feedback useful when learning to write mathematics in LaTeX.
 A text editor that provides lists of mathematical symbols:
I use WinEdt, which has a GUI for many mathematical symbols.
But many text editors provide such support.

Codecogs has a real time online LaTeX equation editor.
 Uni Colorado provides a quick to load
extensive list of symbols
 Scott Pakin provides a big download with
a comprehensive list of LaTeX symbols

DeTeXify allows you to draw the desired symbol online
and the program attempts to guess the LaTeX symbol.

Tex.SE is a great site for getting answers to LaTeX related questions.
Basic Working LaTeX file
The following provides the simplest of working environments which can be useful when first learning.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\end{document}