i for one had a great time.
pissed on the patio at rusty's, got kicked out and then ran away.
another one of my friends went out with a sharpie and anyone who bought him a shot or drink got to add a letter to "I'm a badass [redacted]" on his arm. Course he had to be carried home at about 9 p.m., but thats part of the fun.
Shots you must do on 21st, prarie fire, aborted fetus, true 3 wisemen (a shot of each of the whiskeys), irish car bomb. stay away from too many bombs, and especially flaming dr. peppers (too many of these and you are in the hospital).
typically you'll never reach 21. if you do you probably took a ton of fruity shots etc or spaced it out properly over the course of a day.
you will get drunk. you will puke. you will make an ass out of yourself. you may pee your pants. just make sure you have people around that aren't gonna kill you, and know when to stop.