What works for me is, after braiding take a small piece of the hair on the end that's not braided and wrap it around the braid and pull it thru, like you would do if you were tying a man's necktie. Then, taking that same piece, make a loop knot that sits as close as possible to the braid. This keeps them from unraveling. I wish I had a better description but hopefully this helps. Its really great for taking down the braid because all you have to do is cut the knot and not worry about cutting your own hair. And it tends not to unravel in between washes.
