In this diagram, I’ve assembled a power source (12-2 NM Cable with a ground) feeding two different three-way switches. These would normally be on opposite sides of a room, staircase or hallway. The switches are shown controlling a light.
Notice how the black wire (hot wire) feeds one switch (connected to the dark screw), the neutral wire (white wire) splices and carries on, and the ground wire (bare copper wire) splices, connects and carries on. The switch then has a red and black wire (travelers) that continue to the second three-way switch (connects to the brass colored screws).
At this switch, the ground and neutral wires splice and carry on to the light. The black wire going to the light is connected to the darker colored screw on the switch. Finally at the light, the black wires tie together, the white wires tie together and the bare copper wire connects to the box and the light’s ground wire (if it has one).
By following these instructions and looking over the wiring picture diagram, installing three-ways should be a snap!