Turn Off the Power
Before beginning any additional demolition, be sure to cut power to the room. A circuit breaker locator is a two-part tool to help you match the correct circuit breaker with the wiring. One part is inserted into the receptacle in question; the other part is touched to the circuits in the breaker box. A light will alert you to the correct breaker. Turn off the breaker, then move on to the removal of all surface-mounted receptacles and wires.
Note: If you're uncomfortable with electrical work, please call an electrician to perform any electrical work.