Ah...the age old question....
A few ideas used in professional industry:
•Something very unique at the booth/table (on display) Can be a unique/new craft idea or just something LARGE and/or UNUSUAL that people might come closer to check out.
•Cute bags that you can GIVE AWAY (no purchase necessary) so people are carrying YOUR ads around the event. (You can get inexpensive kraft paper bags and stamp or sticker your name/logo/info on them if you don't want to purchase professionally made bags)
•IF the venue advertises the event, take out an ad, and have customers bring your ad to place in a drawing for something.
•Give something away--cookies, kisses are fine--but better to have something with your name & phone number on it! (Magnet, pencils, etc.)
Good luck!