Something I learned from snowboarding that can be applied to paintball...dont run into the trees, its hard on the head
But on a serious note, I do alot of volunteering at a local feild, I ref, tech markers, run things, I do anything that needs to be done. We have alot of younger players just starting out, and some other guys that want to get better. Most of them are too shy to ask about tips or tricks. When I have the time or chance, I approach the players and chat them up a bit, and offer some tips and tricks, if they go for it, Ive taken players out to an empty feild and showed them things, show them snap shooting etc. Let them shoot you, this way they have fun aswell as learn.
Unfortunatly, like what the OP stated, theres not alot of 'how to play' guides, tips or tricks. If ya wana get better, go out and play, or better yet, play against better people, it wont take long to figure out to stay tight in your bunker.