how to find which bulb is out on christmas lights

Well, there are a few ways to find which bulb is out on Christmas lights. One way is to use a voltage tester, which is a device that can test whether there is electricity flowing through a wire. You can test each bulb one at a time until you find the one that's not working. Another way is to use a continuity tester, which is a device that can check whether there is a complete circuit between two points. You can test each bulb one at a time until you find the one that's not working. A third way is to use an ohmmeter, which is a device that can measure resistance.