Play a rhythm on your guitar using an easy chord pattern. The chords G, C and D are good chords to start with. Strum the G chord with your thumb in a simple down-and-up strumming pattern, letting the strings ring out.
Establish a rhythm, and play a count of four on each of the chords in this pattern: G, C, D, C and back to G to repeat the pattern. This time, allow the chords to ring on the first beat, strumming down. Then use the side of your hand to dampen the strings, and count three beats strumming up with your thumb. The dampened strings create a percussive rhythm for those three counts. Keep your fingers on the chord as you do this, but release the pressure of your fingers to prevent any notes from sounding.
Vary your strumming patterns, and try muting your strings by dropping the edge of your palm against the strings of your guitar when you change chords, creating a percussive beat in between each chord change. Use this rhythm to create a syncopated feel on various counts of your four beats to create different musical feels.
Add percussive touches by tapping your fingers lightly on the top of your guitar, if you play an acoustic. The hollow body of the acoustic allows you to had a box drum effect between the chords you play, creating additional percussive sound in addition to the percussive strums on your strings.