I usually do an email blitz the day after the show (or that night if I'm ambitious) based off of the entry forms we received. I thank them for visiting us and let them know that we are available for their date. I usually throw in a show special and let them know we'd be happy to meet with them.
I send out a slightly different email usually to brides we get from the list but that didn't register with us. It's a little tricky because I don't want to thank them for visiting our booth if they didn't. I usually say, "Thanks so much for attending the Whatever Bridal Show last weekend. We hope you found many vendors that you were looking for. If you are still looking for a photographer we are open for your date and would love to meet with you blah, blah, blah."
Hope that gives you something to go on.