Watch the Rhythm Techniques online guitar lesson by TrueFire from Play Acoustic Guitar 4: Rhythm Approaches
In this section, Vicki Genfan steps you through 13 techniques and harmonic approaches for transforming common chord progressions into compelling rhythm parts. Genfan covers changing tempo, changing time signature, changing duration of chords, finger picking, strumming, plucking, harmonics, relative minor substitution, color tones, power chords, and other approaches that will spice up any of your rhythm parts.
TIP! When you start to work on rhythm parts, remember that the number one thing you should be concerned with is staying in time! This might sound obvious, but sometimes it is easy to get distracted by trying to get a cool move or technique down and we forget about keeping it in time!
So always work on a rhythm part slowly at first, using a metronome to make sure the whole thing is staying in time. If you find one part where you keep losing time, then stop and just work on that part until you get it solid. Remember, rhythm is built from the ground up - so make sure you lay the foundation of a groove before you start to worry about all the fancy stuff!