ok, a 3way switch has three screws, 1 of them says on the side of it common, and its a different color than the other two screws, u have to find the wire in each bos that is the power and the switch leg for those lights. The other two wires are travlers they just attached to those other two screws. I f u buy new 3 ways, on the new box they come in there is a wiri;ng diragram that will help u. A 4way just switches the travelers and the screw up people do is they mix the wires, on the switch has printed in and out on it,from one set of wires goes on the same end and the other two go to the other screws on the other end making sure u have the same color wire fron each different sets on the same side of the switch. good luck take ur time its not all that difficult.