As I just went to the one in Lancaster, PA and going again tomorrow, my tidbit is to know your prices. They can vary so much from one booth to another, so keep in mind what the shops around you charge as well as online prices.
You can make a wishlist of sorts to keep better track, either for what you see there and want to check for cheaper prices or bring along a list with the cheapest price to decide if you want to buy it there.
Above all else, just have F-U-N and take lots of pictures of the quilts.