Hello. There isn't really any secret to it. You'll have to take your volt meter, start at the fuse box, check both ends of the fuse to see if power is actually passing through it, move around the circuit in steps, checking to see if power is making it to that point, and go until you find the point that power is not making it past, and fix whatever it is that's interrupting the circuit. If power is making it all the way to the bulbs, then you ever have a ground problem or the bulbs are bad. Hope that helps.