Also, don't drink or smoke in the booth. Don't bring a phone into the booth. When you're on the phone, you discourage people from entering your exhibit area. If there is a product to demonstrate, let them practice prior to the show. This gives them something tangible to strive for during the event.
Salespeople tend to like to bond with customers.
While that's fine with traditional selling, it's deadly at a trade show. Train your people so they feel comfortable giving a quick presentation and then moving on to the next person. Don't let your booth staff improvise. Have them memorize a sales spiel so they can efficiently and effectively convey your message. Set up a system for qualifying leads, and train your people in using it.