If its a certain manufacture having a demo day at your local mountain.
Basically they will set up tents in the parking lot, with usually their whole line up. If it's a brand like burton - they will usually have boards and bindings to demo.
So you just walk up to the tent, preferably with your boots on and bindings in hand. Most will require a driver license and a credit card - they write down your name and what board/time you took out. And you just hop on the lift, ride for usually about 3 runs/hour depending on how busy it is. If they are people waiting, try not to take long. Then you bring the board back and try another.