You can either leave the ends long so they drape down, or you can keep them short so that the focus is on the bow. My one recommendation would be to cut the ends in a way in which the ribbon doesn't come apart. My favorite way to cut it is like this:
2. Then you fold it in half width ways
3. Cut it diagonally from the tip or corner to the inside of the ribbon
4. This is what it should look like
5. And you finish with the cutest ends ever!
Here is a couple of outfits in which I have used this tip: