How to learn LaTeX
How I did it: I used the internet. There's a multitude of documentation, tutorials, and discussion groups out there with the answers to all your questions. One particularly helpful document is the "not so short introduction to LaTeX" which can be found here.
Lessons & tips: Just start messing around. If you don't know the right code, take a guess and see what happens. If it doesn't work, or you have no idea, google it.
Resources: I found TeXmaker to be really useful. It has shortcuts to a lot of common sequences, and an easy to read menu for mathematical symbols. And it's free. You can find out more about it here: http://www.xm1math.net/texmaker/