Yes. Body shots as a courtesy, although headshots do happen from time to time so don't think you can bob up and down like it's wack-a-mole because you *will* get shot. Ballistic rated googles are a must and outside of that you can wear whatever you desire. Play in shorts for all they care -- it's your body.
Generally speaking, most people will be wearing goggles, camo/dark colored clothing, tactical vest (to look the part, to carry magazines and for some added protection) and a cap/boonie hat/helmet. For indoor/CQB games, you'll also see a lot of people wear metal mesh lower face masks because the last thing you want is to turn a corner and shoot someone (or get shot) and chip a tooth (it's happened before). Some will wear a shemagh for face protection instead. I have one too, but it's to protect my neck/throat. Also gloves are recommended because getting shot in the finger/knuckle around a corner hurts like a bitch.
@ Leroy: it hurts differently than paintballs. Paintballs compress and explode with paint so you're left mostly with bruises if anything. BB's on the other hand, don't compress but have a smaller contact area so they're more like stings. You'll get welts and bleeders mostly.
I'm not sure what a paintball can do to a full can of coke, but I can shoot thru it with my gun and it's only at 320fps (limit for CQB is 350)
EDIT: as for ear protection, the straps from the goggles/facemask usually covers up the ear quite well, but it's never been a problem thus far...