Take your own food if you can. I agree with Marijeaux in that the food is expensive and poor quality. I take a great big bag, and we all put our lunches in it. When I get there, I check my bag with my food upstairs at the bag check , then at lunch, meet up with friends, get the lunch bag and eat. Then we load up the lunch bag with our purchases (so we don't have to carry them), recheck the bag. And shop until we drop, or the festival closes, whichever comes first.
Make sure you get your friends cell phone numbers because it is so big, you can't find anyone.
Wear comfortable shoes, bring some aspirin, and carry as little as possible in your bag. I don't even take my purse in. I need my phone, aspirin, credit card and some cash. That's it!