I recommend bringing money if you plan to buy things at the dealer's room (DVDs, shirts, figures, posters, wallscrolls, plushies, etc etc). They can get pretty pricey in there, just so you know. From what I recall, they're usually retail prices and higher.
As for preparing yourself, get some sleep the night before. If you want to try and see as much of the con as you can in those three days you'll be moving around a lot looking for the right rooms (I got a little lost last year looking for a couple places, running to and fro).
Cosplaying is actually pretty fun, despite what some AMV editors might say.

People will run up to you and act excited that you dressed up as their favorite anime character from their favorite anime or whatever. When I dressed up at SakuraCon 03 (I was Terry Bogard) tons of people wanted me to pose for pictures. I won't lie to you, I loved the attention.
Most of all, don't let the idea of crowds get to you, if it does at all. Outbursts of personalities and humor make great con memories (for both you and whoever happens to be around you at the time). Just enjoy yourself; that's what your there for. Hope to see you there.
/end lecture
