I'm about ten cons in right now, and I can tell you, the first one I went to, I didn't have that good of a time. This was because I was tragically unprepared for what I was getting into. A guy I was dating at the time bought me a registration for Otakon 2005 as an early birthday present. That was my first con: Otakon.
For lack of better terminology, it was pure culture shock. I wasn't ready for the crowds, the cosplayers, the walking...and so on and so forth.
You don't have to prepare your friend for anything because you've already done said preparing.
You're breaking the con virginity by introducing him to something on a smaller scale.
Good luck and I hope he has a good time.
