[SteveC7010]

If it is a standard wall mount for a flat screen TV, then there should be two strings or straps hanging down behind the bottom of the TV. They may not be visible from straight on, but if you can look up from the floor or feel back there with your fingers, you should find them. They each control a spring loaded latch on the mounting rail.

Pull them both down at the same time, and pull the bottom of the tv out from the wall slightly (an inch or two is fine) and then lift the whole thing off the mounting rail.