Watch the Two Chord Vamp Etude Level 3 online guitar lesson by Vicki Genfan from Open Tuning Handbook: Rhythm

Find your chords. Make sure you only move two fingers when changing chords! Next, make sure you have the rhythm down. Finally, bring in the body percussion! If you're worried about using your nail on the guitar finish, you can use the fleshy part of your finger. It's important to keep your right hand fluid and relaxed while playing the body percussion. Follow along with me on the video to make sure you've got the rhythm right! Such a simple progression, but it's loaded with cool stuff.