The best way to decorate a Christmas tree with ribbon is to start by attaching a string or hook to the top of the tree. Then, hang a loop of ribbon from the string and secure it in place with a small ornament or bow. Continue adding loops of ribbon down the tree, spacing them evenly apart. Finish by tying a bow at the bottom of the tree or at the base of the trunk. You can also add small ornaments or other decorations to the loops of ribbon for extra flair.