Bridal Shows can be very overwhelming for Brides and Grooms. My advice is to use the time to get ideas and information. Gather as much info and talk to as many vendors as you can.
While at the event be sure to set aside the cards and info of the vendors you were impressed with. If you don't do this it may be hard to remember the specific vendor you liked.
After the show go through your information and start calling back your favorite vendors to ask more detailed questions.