I agree with MrsOpie to a point but part of the reason the brides come to these things is for the freebies. Think of your job at the expo as not to book brides but to get them to come to your table, pick up your info, and take it home and compare it. Your booth is your cover letter and your services are your resume, so to speak.
If you have a great giveaway that has them coming to your table to pick it up, something they will wait a minute for, see other people with and ask where they got it, etc., then you've done your job very well. If you have something that you can attach your info to to ensure that they are getting it, too, then that works well.
Draws are great for gathering contacts, but brides will just as quickly enter a draw for a set of photo frames as they will a draw for your services. If you go that route, be sure to have someone there to greet each person and pass them your information.