You mean convention right? Didn't think you were going to become a priest
Any ways, here's some tips:
1. WEAR DEODORANT! Cons can get pretty hot, and I'm sure you don't want to end up smelling of BO. Oh, and you WILL run into someone who hasn't bathed in a few days, but its the risk you take going to a convention.
2. Bring money. Lots of it. There's going to be things that you can get at a con that you either can't get anywhere else, or are extremely hard to get outside of a Con.
3. Bring your own food and water, especially water. Drinks and food are expensive at cons, so be prepared.
4. Bring bags and things to carry your loot home, the bags they have at cons often aren't very good and will rip or tear easily.