Carry a drink (water or pop is recommended over alcohol) in your left hand. This keeps your right hand available for shaking other people's hands while giving your left something to do. This is a social business event, after all; the trick is to look social while being business.

Tip: Don't drink alcohol. Unpopular idea, we know, but one drink is enough to cloud some folks and send them slurring. If you want to drink, you might want to change venues. Better to not be seen than to leave the wrong impression with the wrong person.