Check in early or late. I picked up my badge on the second day and completely avoided any and all lines. I hear the folks who arrived on the first day had to battle epic crowds (one of the few things that instantly gets me in a bad mood).
Introduce yourself to people. I thanked/spoke with editors who had published my work in literary magazines, chatted up folks running tables for journals I really admire, and mingled with professors, writers, and publishers who seemed cool. Who knows when a connection you make will turn into a career opportunity?
Exchange business cards. There were way too many names and faces for me to recall even a tenth of the people I met, and I'm sure everyone else felt similarly. Cards help refresh your memory and provide much-needed contact information.
Go to the hotel bar. Everyone worth talking to is there. Everyone not worth talking to is somewhere else. Everyone who doesn't want to talk to anyone is holed up in their hotel rooms.
Budget carefully. Many writing conferences have a lot of awesome books for sale, and the temptation to buy everything is pretty strong. If you're not paying attention, you could end up spending way more money than you intend (and will then have to lug 30 pounds of books home with you). That said—
Make sure you walk the floor on the last day. In this case, many publishers wanted to unload as many copies of books/journals/magazines/t-shirts/&c as possible so they wouldn't have to lug/ship them back. This resulted in a lot of great deals (and even free stuff!) on the last day of the conference.
Were any of y'all at AWP, as well? If so, please feel free to share your stories in the comments!