Best advice I was ever given -
Grab a gun
BB's (good quality as mentioned, BB Bastard is awesome)
Hicap (Bleh, they usually suck ass but for your first game whatever)
Goggles (Depends on where you go to play)
Water & Food (Always bring extra, you never know how bad you'll work yourself out)
Have at 'er!
You'll learn what you need from there and improve as you go.
"what should i know so that i dont look like a complete noob?"
Nothing, you are what you are at first
The only way to fix that is get out to a game and learn.