How do I wire two switches to control the same light? What you are really asking is “How do I wire a 3 way switch?” "What does a 3-way switch wiring diagram look like?" People seem to get very confused over how this is done. However, if you break it down, it is really very simple to understand.
What does a 3-way circuit do?
A three way circuit allows a person to control a light from two locations. This means that you have the ability to turn the light on or off from either of switch locations, regardless of the position of the other switch. However, unlike the standard 2-way switch where up is on and down is off, the positions of the switches on a 3-way switch is not always indicative of the of the light being on or off. See the diagrams below for an explanation. Click on the 3-way switch wiring diagram shown below for an enlarged drawing.
2-way & 3-way switches
How do 3-way switches work?
Switch selection is where most of the problems occur. You must use three way switches. This means that the switches that you are using have 3 terminal (not counting the green ground screw), instead of the usual two found on the standard 2-way switches. One of these terminals is usually identified as Common and is a darker color (black) than the other two. This Common terminal is not to be confused with the ground (green). The common terminal will always be electrically connected to either one of the other two terminals (we will call them A and B). This means that when you toggle the switch one way, Common terminal and A terminal will be electrically connected. If you toggle the switch again, Common terminal and B terminal will be electrically connected. Read this artical on switch selection if there are more questions about types of switches.
Now that we understand how the switches work, “How to install or how do we make the 3-way circuit work?” A three way circuit consists of incoming power, 2 three-way switches and a light. Although the circuit can be physically laid out in many similar variations, it will always follow this same concept. The neutral and ground wire will start with the incoming power and will be terminated at the light. They may be spliced together, but will never be broken by any switches. The hot wire from the incoming power will be connected to the Common terminal on the first 3-way switch. Two wires will then leave the A and B terminal on the first 3-way switch and connect to the A and B terminal on the second 3-way switch. These two wires are often called travelers or runners and one of the two will always be hot. The hot traveler will be alternated on and off by switching the first three way. The Common wire on the second 3-way switch will then connect to the light. Switching the second three way will connect one of the travelers to the output wire connected to the light.Click on any of the following 3-way switch wiring diagrams shown below for an enlarged view of the wiring diagram.
3-way switch circuit
This should complete your circuit. The following wiring diagrams will illustrate of few of the configurations that you may run across in real life situations.
3-way switch circuit powered via first switch
3-way switch circuit powered via light
3-way switch circuit powered via light
3-way switch circuit powered via second switch
The following three way switch wiring diagram does not have incomming power connected to one of the switches common terminal. In this configuration, a hot wire is located at each of the switches.
3-way switch circuit powered at both switches
If you notice that the wire is silver in color, which probably means that you have aluminum wire instead of copper wire. If this is the case, make sure that you are using aluminum rated switches as most are rated only for copper. When ever a white wire is used as a traveler or a hot wire, it needs to be identified as a hot wire by marking with electrical tape. Always obey and abide by the NEC and local electric code
To see a video demonstration of wiring a three way switch click next below.
Electrical 
