Using the maple leaf template I traced for the thankful banner, I sized them to fit some tags I already had (bought in an office supply store) and sandwiched the tag inside two leaves.
here. The left leaves are a mirror image of the ones on the right, so when you cut and sandwich, the cutting lines will be hidden. You also could simplify this by punching a hole in a single leaf to tie a string on.
The tree sits in the middle of our table, with leaves and a metallic Sharpie next to it. Anytime someone is moved to do so, he or she can add a leaf to the tree.