I acquired a pair of jeans for 97 cents a little while ago from Old Navy. They were a bit too big for me so I knew they'd be perfect for a DIY project. I decided to turn them into shorts, distress them, and add some spray paint just for funsies.
To turn them into shorts, I laid an existing pair of shorts that I liked the length of on top of the pants as a guide of where to cut. If you're going to roll the bottom of the shorts, be sure to add a few inches to the length. It's always better to start longer and cut more off as you go until you reach the desired length so err on the side of caution here. I followed this method for distressing the jeans. I got a bit lazy with it so my distressing is more minimal at the moment, but I figure they'll get more distressed over time. To add to the worn/distressed look I haphazardly spray painted sections of the shorts. There's really no method to this. The more random the better. After the spray paint dried completely, I rolled the bottom of the shorts twice and hemmed the sides and the middle of the back to keep the fold in place.