Good question... This will be my first Summit too but I've been to plenty of ad:techs. If it's anything like ad:tech (but geared more towards Affiliates) I would set up meetings with the companies that you already do business with, meet your contacts within those companies in person (it always helps to put a face to a name), figure out how you can do more business together over dinner and some drinks!
Many times you'll meet new contacts through the people that you already work with. Go to the parties, find the right places to hang out and just enjoy it. I wish I knew more about Vegas and the Summit so I could help you with the parties and places to go but maybe someone else can point us in the right direction!
I've found that if you just go with the flow, have fun, talk to people, drink and party you can't go wrong. You'll be surprised how many people that you meet at these events will become good friends and contacts and you'll be able to work together in many ways. Good luck and have fun!
oh yeah...just like UnripeArbiter said bring LOTS of business cards - they disappear too fast and you can never have enough!