Adding onto #3 from BellaDeb's Trade Show Tips - Bring the �essentials�.
Giveaways with your contact information is important but if there is anything you can give away that is practical, helpful, and/or useful, that tends to be a more effective marketing tool. For instance at a service sellers show I did once, I gave away a kids daily planner (I'm an organizer). I ended up getting some clients who later came across their kid's planner and found my contact information inside!
Here's another idea just to help get your creative ideas going. Last month I attended a concert with my kids and a radio station was giving away CD openers. (Small plastic items which quickly yet safely slit the strong white packaging strip on a new CD). Sounds silly, but we actually use it and guess what? We've tried the radio station too!
Clever ideas for giveaways can be effective. Try to think of something different and that people will actually use.
Hope that helps!