[header] How to hang lights on a christmas tree [title] Plug the lights in to make sure that each bulb works. [step] If a few don't, try tightening them-they may not be broken after all. Once you're confident they work, unravel them. 
This way you don't spend minutes unraveling what you don't use. [substeps] Spend a couple of minutes tinkering with them, and then if they still don't work, throw them out.