Comfortable shoes and extra cash are a good start. Notice I did not say a "little extra cash." :) Most vendors at quilt shows will also take credit cards.
When I go to a quilt show, I find it useful to wear hiking pants with lots of pockets. I bring my wallet keys and some water. Also, I usually pack a lunch and leave it in my car in a cooler. Much better than what is available at the show.
If it is a large show, it can be nice to spend two days viewing it. I tend to get visually overwhelmed at some point. If I have time I like to go back and look at the quilts that really impressed me.
Have fun!