The best way to fix half-out Christmas lights is to check the connections and replace any burnt-out bulbs. The first step is to check the connections by unplugging the lights and examining each bulb and wire. Look for any burnt-out bulbs, loose connections, or damaged wires. Once you've identified the issue, replace the burnt-out bulbs with new ones. If the connections are loose or damaged, tighten them up or replace the affected wires. Finally, plug the lights back in and test them to make sure everything is working properly. With a little time and patience, you should be able to get your Christmas lights working again in no time!