The most important thing to consider when making a Christmas tree on the wall is the location. You want to choose a spot that's flat, free from obstacles, and has enough space to accommodate the size of your tree. Once you've chosen the spot, you can start by measuring out the area and marking it with a pencil. This will help you determine the size and shape of your tree. Next, you'll need to gather your materials, which should include some plywood or MDF board, a jigsaw, and some paint or wallpaper. Once you have everything ready, you can begin cutting out the shape of your tree.