I've never actually hung Christmas lights before, but I do know a few tricks. First, you'll want to make sure you have enough lights and extension cords to reach all the way across the window. Then, you'll need to measure the length of the window and calculate how many lights you'll need to cover it. Once you've got that figured out, you can start by attaching the first light string to the top left corner of the window, and then work your way down to the right. Make sure to leave enough slack between each string so that it hangs straight.