security is pretty lenient (at least the ladies are). they'll take away the usual stuff: drugs, weapons, pens, markers, open cig packs/gum/candy. just don't be stupid and you'll be fine.
FYI, there are cops and emergency service personnel waiting outside at all times so if you do get caught up, you will be handed over to local law enforcement but don't let them freak you out. like i said, just be cool and don't be stupid and try to sneak drugs into an event like this. plain clothes officers are patrolling around inside so don't do anything retarded while you're in there, either. my advice: BE COOL and you'll make it through the night without getting into trouble. you won't, however, be able to avoid the rave rain (sweat dripping from the ceilings/walls cuz it's so hot/crowded inside), the totally wasted teens and those assholes that run into you and don't even apologize. it's all part of the experience i guess. have fun!