First, don't listen to anyone who hasn't actually gone playing. Especially don't listen to PennState:
"3. Be a liar. Say "don't shoot, I am on you team" then unload a hell of ammo into the gullible opponent."
Thats a guaranteed way to get your ass kicked, and then banned from the field. I hope he was being sarcastic, because thats a pretty retarded thing to say.
I'm assuming that your going to be playing in a big field/forest, rather than a small arena (speedball).
Clothing/Safety:
Cammo and dark clothing are good. Be sure to wear something to cover your nuts, being hit in the nuts really sucks. Paintballs don't hurt, unless your expecting to get hit, or your a wuss. Don't wear white socks, they ruin your cover. If you can, get a neck protector, or a shirt or jacket that has flip up collars. Wear a backwards baseball hat, then put your mask on. It gives the mask a better fit, and it protects the back of your head also. Thats about it for clothes.
Strategy:
Try to stick to someone who is more experienced (or who has a kickass gun) to get the hang of things. If its a big field, the best thing to do is to walk the tape, which means moving up the side of the field, right next to the boundaries. The other team never seems to look behind them, so ambushing/swiping their flag is pretty easy after that. Unless your l33t like Suicidal, then you can run in like a Juggalo and start kicking ass.
Oh, and fat kids are the most fun to shoot at. Aim for their love handles and they will cry like little girls.