I came up with this exercise years ago while trying to compose a piece of music (which never got composed) and have been learning from it ever since. I'll go through a number of possibilities that I've come up with, but I really hope you are encouraged to take this exercise and make it your own. Find ways to challenge yourself and you'll be amazed at how much you can improve.
I've taught this workshop a number of times and it has been my favorite workshop to teach because participants contribute so many interesting ideas. In 2016 I'll be doing a workshop similar to this, but I'll include some different types of chords, some double strokes, and we'll be working in 6/8 meter.
If that is something you're interested in learning, find out if I will be at a festival or club near you. I will be releasing that video series (for a fee until I retire the workshop), or you can contact your local club or festival coordinator and let them know you're interested in having me come to teach.