Dealers in all types of show settings realize it's customary for shoppers to ask for reasonable discounts. Be aware, however, that some will welcome it more than others. Occasionally you’ll run across a show dealer who demands full price with no exception, and the way they respond to your request for a better price may be nothing short of rude. They'll seem insulted that you even thought to ask for a discount. The hard part about this is that you don't know how they're going to react until you go ahead and ask.
In these instances, you can choose to begrudgingly pay the asking price and reinforce the belief that they don't have to consider discounts (or even be polite about it!) to make sales. Or, you can simply move on and do business with someone who knows how to treat their customers with respect.
Most dealers, however, will treat you respectfully when you show them the same courtesy. Expect 10-25% off when you ask for a better price and make a counter offer, when needed, and you'll usually strike a deal in these venues. Know that checking back with a dealer at the end of a show if a piece is still available never hurts. Sometimes they'd rather sell at a discount than haul a piece back to their shop.
Take a look at more strategies for haggling in a number different selling venues: