I don't do fairs, but have friends who do, and I've been to several.
1. Use HUGE photos on easles. These photos should be very dramatic, or very colorful.
2. Have a slideshow going on a laptop of your very best work.
3. Bring samples of your albums, prints, and gallery wraps if you carry them. You can't sell what you can't show.
4. DON'T do give aways for leads. It devalues your work, and no one wants to be spammed to death. I learned this lesson from a photog friend who tried. She got nothing but bogus e-mail addys, real addys, and faked phone numbers.
5. Do have a sign in wedding date sheet. That way brides can see that other brides are interested in HER date. That will put some immediate actions in her mind.
6. Dress very professionally. Seems like a simple thing, but I've seen many mistakes here. Dress for your target audience. If you do funky stuff, dress funky, but PROFESSIONALLY.
7.Give them something they can take home that they will really use. Forget key chains and pens, give 'em a CD of a sample slideshow or a nice postcard featuring your work.
Hope that helps, and the best of luck to you!