One problem with baggies is lack of ventilation. After reading about it in a book or magazine a few years ago, I started using plastic 1 liter bottles (saved from buying bottles of water or soda.) Cut the bottom out and the bottle fits quite nicely just inside the perimeter of a 6" pot. The open neck allows for sufficient ventilation while keeping the humidity high, and doesn't collapse against the stem or leaves, knocking the cutting over.