I'll be there! Gen Con rocks. I'm already counting the days until my kid's old enough to go and enjoy it.
For first-timers, although this is rather bland advice, I'd say the most important thing is to find what works for you. There are many ways to enjoy Gen Con: old friends, new friends, once-a-year friends, new games, old games, old games in new ways, seminars, "celebrity" sightings, awards, the dealer hall, Trade Day/Teachers' Day, the Ram, True Dungeon, and a ton more.
For less bland advice, I'd say: build up your endurance. Get tons of sleep the week before, get in shape, whatever you need to do. Because starting Wednesday (there are always games on Wednesday, don't miss them), you're going to want to get by on 6 hours max. sleep until Sunday night. Less if you can. It's that good.