This is kind of a lame tutorial since it is pretty obvious what you need to do. You start out with a pair of pants that you just don't like the length of. Mine were given to me free by a friend and since they were a petite size, they were way to short.
Fold your pants in half and make sure both legs are lined up exactly. I cut just below the knee which gave me plenty of fabric to roll four times. The more times you roll the material up the leg, the more secure it will be.
There you have it, a new pair of bermuda shorts!