When you install Christmas Lights you have to be ready to troubleshoot and repair them before even installing them. Troubleshooting requires a selection of bulbs in the sizes used in your display, flasher bulbs if used, and some of the mini fuses used in some plugs. Sometimes a small screwdriver and needle-nose pliers may be needed.
When you take the lights out, before installing them stretch them out, give the string a visual inspection correcting any problems you see, then plug the string in to test them. The lights are far easier to test and repair stretched out like that than when installed. If the entire string of lights is dead look for problems at the plug or, the fuse on the plug. If a single light is out or several scattered lights are out it is more than likely burned out bulbs. If you have mini lights make sure that you replace the bulbs one at a time and the lights come back on after each bulb is replaced. With the mini lights a burned out bulb does not affect the others but when a bulb is removed or, not in the socket properly part of the string or, the whole string may not light. If a mini light string is completely out or, large sections are out remove each bulb and make sure the wire contacts are placed correctly then reinsert fully into the socket, when you find the one that is loose or, plugged in wrong the string will come back to life.
With the older intermediate base and candelabra base lights some times the glass part of the light comes loose from the base making it difficult to change the bulb. When loose bulb breaks off from the base make sure the string is unplugged, then jam either a straight screwdriver or, the spread tips of the needle nose into the broken off base then turn it out with the screwdrivers or pliers.
Installing Christmas lights requires some planning. In days of old the light strings were often rated indoor only or inside and outside use. Today the distinction has largely been removed with most lights being sold having the inside and outside rating. Check the UL rating tag to be sure of the lights ratings, never use lights outside that are not rated for outdoor use. Extension cords have similar ratings and should not be used in the incorrect application.
Plan your display making sure that you have enough lights to cover your intended display. It is far better to have to bunch lights closer together then to come up short. People who set up lighting displays even very large ones, tend to reuse the display from the year before and add onto it each year. Because of the reuse each year many homeowners tend to not use the commercially available clips that attach on shingles, gutters, and siding, opting instead to use stronger more permanent fasteners which strategically located can hold up large amounts of the display while remaining inconspicuous in the off season. Permanent fasteners constructed of stainless steel or, brass can remain useful for many years without any rust staining. Nylon zip ties can also be used to attach around existing structures such as gutters and down spouts.
Planning ahead and installing receptacles in locations where your display will need power is also a good idea, which will keep extension cord use to a minimum. These outdoor receptacles can also be placed on timers which can turn them on and off for you. Enjoy setting up your display and plan ahead for expansion of the display.