[header] How to replace dead christmas tree lights [title] Get replacement bulbs when you buy your lights. [step] Purchase replacement bulbs for your christmas lights at the same time that you buy your string (s) of lights. They are often sold at the same places and you are more likely to find ones that fit the kind you buy at the time rather than months or years later when you need them. 
[substeps] Your package of lights may already come included with a few replacement bulbs. Make sure any replacement bulbs are of the same voltage as the original strand.