I'll be there. I've only gone once before a couple years ago. Not sure what kind of advice to give since I don't know what kind of experience you're looking for.
I'll tell you, though: it will go by fast. Even if you're there all 4 days at the end of it, you'll be wondering where all the time went then shortly after that you'll start going over everything you did and realize you did a crazy amount of stuff. At least that's what it was like for me.
If you pre-registered for any games, be open for changing your schedule. I signed up for a number of games my first time, and I ended up cancelling all but a couple of them. Once I got there I found a lot of other things catching my interest. Number 1 for me is the Games on Demand room (I always forget what hotel it's in). It's all indie & small-press games, but there's usually a couple people there to help facilitate things and a table stacked high with games for community use. Go there, hang out, find something you're interested in running/playing and drum up other interest. Boom! Ad-hoc gaming. That was definitely my favorite thing. I met a lot of cool people, chatted with a number of game designers, and discovered some great games. One guy ran a couple scenes out of 4 different games in 2 hours -- all 4 games were interesting and I absolutely fell in love with one game (Misspent Youth
) and ended up doing a bit of playtesting for the designer.
The main floorspace (where all the merchants and such are) is huge. Don't be surprised if you don't see everything. I remember before the doors opened I had a number of things I was excited to see. But then I just went in and wandered around aimlessly for the most part. At the end of the weekend I realized there were a couple of booths that I didn't even see. Oops!
I'm not going to tell you how to have your fun, but, for me, gaming conventions are all about trying something new. I'm looking to play games I've never played or maybe even never heard of. I've had friends that play game <x> regularly with their gaming group. Then they go to GenCon and play <x> all four days. I honestly don't understand that. I want to experience what's out there! YMMV
Some advice a friend gave me before my first trip was to try and see a seminar or two. I ended up ignoring him because I just wanted to play. This time around I've signed up for a few seminars that look pretty interesting (mostly by game designers I know). In other words, there's a lot to do that's not gaming so definitely think about checking some of those out.