Last year was my 1st GenCon, and as far as events go, I'd suggest limiting yourself to one preregestered game per day. I signed myself up for 2 each day, then ended up dropping a bunch because I wanted to go to seminars that conflicted with the games. Plus, there are PLENTY of pickup games going on. Even if you don't sign up for any games, there is so much going on at any given time, you'll never have trouble finding something to do. But if you see something that you just have to play, by all means sign up!