On The Lamb Games:
Comfy shoes! If you can afford it, those workshop foampad tiles for the floor are a godsend.
I can confirm this!!! Those foampads for the floor can be picked up at Wal-Mart or Meijer for real cheap. They're in the automotive/hardware department.
Also, keep water handy and some hard candies for your throat. You can QUICKLY lose your voice.
Remember to eat. You don't realize how much energy it takes to be ON for 8 hours straight. Last year, I was pooped!!!
If you can afford it, sign up for the Cheese Weasel promotion (if they do it again). A lot of people will show up at the booth, many just want their cards punched, but they all have to listen to the spiel. We had a lot of increased sale due to this promotion. We sold quite a few books to people who had never heard of the webcomic.
As for other costs, once you see the pdfs, you'll understand why you might need to bring the stuff with you, if at all possible. We're lucky. I live 45 minutes north of Indy so all the product is shipped to me to save money.