Product brochures, warranty booklets and articles written about the product can all be used to prove the benefits of your merchandise. Even catalogs, newspaper and magazine ads help lend credibility to a spoken claim. My wife and I were recently at a street fair, and there was a booth where a young man was slicing and dicing vegetables with a small plastic gadget. It didn't look like much in the box, but the demonstration was irresistible. We are now the proud owners of a new vegetable chopper.
Demonstrations are powerful proof.
Get the customer physically involved whenever possible. Let them touch the item, try it on. Add touch, taste and or smell to that and the impact is increased significantly. The room would be considerably lighter and brighter. When you create pictures in your customers' minds, your customers sell themselves.