A dimmer switch is great for taking control over the way a room is lit. It gives you the ability to make subtle changes in light levels—to set the mood in a dining room, lower the levels in a child’s room, or even give you flexibility with outdoor lighting. A dimmer also saves energy by cutting down on electricity usage and extends the life of most light bulbs. Putting one in is simple. Turn off the circuit breaker at the electric control panel, and then just follow these easy steps:

1) Use a screwdriver to remove the wall plate. Then unscrew the switch mounting screws.
2) Grasp the switch by its flanges and gently pull it straight out of the mounting box. With a neon tester, double check to make sure the circuit wires are not electrically charged. It won't light up unless there is still power in the circuit.
3) Unscrew the wires from the switch terminals. If they are poked into holes in the back of the switch, use a small screwdriver to release them. Straighten the ends of the wires, or, if possible, snip them off and strip the ends again
4) Use lineman's pliers to twist the bare end of the green ground wire together with the bare copper ground wire in the box. Then use a wire nut to further connect the dimmer’s ground wire to the circuit's bare copper or green ground wire.
5) Then connect one of the dimmer’s black wires to each of the two black wires in the box.
6) Make sure the connections are tight, and then carefully push the wires into the box to make room for the dimmer. Position the dimmer, and screw it to the mounting holes in the box.
7) Then replace the faceplate. Turn the power back on at the electrical panel, and then try it out.