If you find a particular dealer pleasant, be sure to ask for their business card. At least around here, most of the dealers will have cards.
Remember the rules of being a good customer:
1. Ask before touching. "May I see _____?"
2. Verify the firearm is unloaded.
3. Keep the muzzle pointed in a safe direction, usually down.
4. If you want to look through the sights, keep the firearm pointed down in a safe direction when you do.
5. Return the firearm with the muzzle down and action locked open. (Might be my paranoia, but idiots occasionally load guns at gun shows and return them. It's happened here in PA.)
6. Say thank you.
If, after handling, they ask if you want to buy it, ask for the price and a business card if you think you might want to purchase it. Jot the price/model down on the card, and tell them you're interested but need to think on it.
Before buying anything, you should check current pricing to make sure you aren't overpaying. Don't worry about losing out on the gun, there are plenty more just like it. Once you know its worth and what you're willing to pay, go back to the guy and start dealing.