A two-way switch on a light fixture can come in handy at times--like if you need to go down a dark stairwell, but not back up right away. Or if you come into your house from the garage, you can flip a switch in one location to turn on the light, then turn it off from another location. Here's how to wire a two-way light switch.
Buy special switches for this application. They will have 3 poles, or terminals, on them instead of the normal 3. They will not be marked for "on" and "off."
Bring the power to the switch nearest the breaker box with regular two-wire house wiring cable. Ensure it is the right size wire for your application, normally 14 gauge wire. There will be 3 wires in the casing, one encased in black plastic, one encased in white plastic and one bare copper wire.
Run a wire cable with 3 wires, plus the ground, from one switch location to the other. There will be a wire encased in black plastic, one encased in white plastic, one encased in red plastic and a bare wire in the cable.
Place another two-wire cable between the second switch and the light fixture.
Apply the black wire from the electricity source to the gold, or hot terminal on the top of the first switch. It will usually have "black" embossed in the plastic switch housing near the terminal.
Splice, or tie the white wire from the source to the white wire you ran to the other switch and secure with a wire nut.
Terminate the black wire that runs to the other switch to the terminal directly below the first black wire, and the red wire to the gold terminal on the opposite side of the switch.
Wire the second switch with the black wire from the first switch terminating to the lone terminal on one side of the switch, and the red wire to the terminal directly opposite that one.
Find the two-wire cable you ran from the second switch to the light fixture. Terminate the black wire to the hot terminal on the light fixture, the white wire to the neutral and the bare wire to the green or ground.
Twist the remaining 2 white wires at the second switch together and fasten with a wire nut. Secure all switches and the fixture in their boxes and apply the power.
Check local regulations on permits and laws concerning home wiring by non-licensed professionals. Some prohibit anyone but licensed electricians from doing electrical work.
Always ensure the wire and appurtenances you are working with are not energized. Check for current with a voltage meter. If anyone else can access the electrical service panel, ensure they know you are working. You can lock the panel or post a sign on it so the piece you are working with is not accidentally energized. Don't use metal ladders when working near electricity and ensure your working surfaces are dry.