When trying to shorten an artificial Christmas tree, the first step is to determine which part of the tree needs to be shortened. Once the desired length is identified, use a sharp pair of scissors or pruning shears to cut off the bottom branches at the desired height. Be sure to cut at an angle so that the branches can easily slide over each other when placed back into the tree. It may also be necessary to adjust the tree's position slightly after the branches have been cut, so that the tree stands straight and balanced.