There’s a very good guide to BBcode in the FAQ section, as ezpete said.
I’ll just go ahead and link it for you.
There’s also a list of BBCode colors too. I, uh, made a contribution to that myself.
Personally, I use a shitton of BBcode. It’s very useful for painting the fourth wall, and I’ve seen a number of other writers color-code their fluffy characters’ dialogue with it.