To purchase a Christmas tree, you should first decide when you want to put it up. If you plan on getting a live tree, it's best to purchase one shortly before you want to decorate it. If you're planning on using an artificial tree, you can purchase one earlier in the season, so you have plenty of time to set it up and decorate it. Once you know when you want to put up the tree, you can begin looking at different options for purchasing one.