I do a very basic job. First, I cut them off (trying to get them straight an even. . . I am not a perfectionist so I just eyeball it).
Then I fold the ends under about a 1/2 inch and iron them so that I have some sort of line to go off of.
If I want them to be extra nice, I will fold them under twice so that they won't fray at all. Otherwise, I just fold them under once if I am short on time and if they are just for summer play anyway.
Next I sew around the bottom. Twice. They seem to lay flatter and nicer when I stitch twice around.
And that's it. :) Here are a few of my finished products:
One reason I like to cut off jeans is so I can decide the length of the shorts--especially for my girls. I like them to come to the knee. We aren't short shorts people. Another reason is obviously to save money. Many times, money is tight around the start of school (along with the rest of the year ;) so these will end up being their school shorts, too. Once they are hemmed up, they look very nice.