Wiring a three way switch, explained verbally, and shown with diagram.

Easy way. Simple three way

1. Place the boxes on the wall where you want the switches.
2. Picture them as a straight line and pull 14/3 between them
(note one box has two ends. This will be the four way location)
3. Put power and neutral in one box
(pull a 14/2 from a 15 amp receptacle or breaker. Black will be power, white will be neutral, and bare will be ground)
4. Now go to the last box and pull a 14/2 to the lights.
(this is a switch leg)
5. At the light all will match the fixture colors
6. At the switch leg end tie all of the whites together, and the grounds separately together.
(leave a 6" ground tail to attach to the green screw of your three way switch)
7. Take the black of the switch leg and place it on the black or common screw
8. Take the black and red of the 14/3 and place them individually on a separate silver screw.
(these are called travelers)
9. At the center box (with two 14/3 wires) attach all grounds with a tail to connect to the green screw
10. Tie the two whites together as all they will do is pass a neutral to the light
11. Look at the back of the four way switch ..(.Levi-ton uses the two top screws as inputs and the bottom as the other input, where pass and Seymour uses the left side as one input and the right as the other input) An input is the black and red wire coming out of the same sheath. Make sure that any wire on an individual input comes from the same white casing as the other on the same input)
12. At the power end the whites tie together passing neutral to the light at all times
13. The grounds tie together passing a grounded conductor through each switch to the light at all times (also to the switches green screw)
14. The black of the 14/2 Power wire attaches to the black/common screw
15. The red and remaining black each attach individually to the remaining silver screws

See power goes into the three way switch and follows the connected patch down one of the two travelers at any given time. Any of the switches stir up the pot in a manor to either connect or interrupt the power source headed for the light.

Three way switch powered at light box, with 4 way added.

Three way switch powered at light box

Three way switch when powered at light box