Watch the Tenochtitlan online guitar lesson by Stephen Bennett from Harp Guitar Repertoire
The percussive taps on the instrument are part of the music, not afterthoughts. There are different tones to be gotten out of tapping the body of an instrument so experiment a little with your own. I am using the sound of the top as one sound and the bottom end of the guitar as another. You'll probably want to experiment with different specific locations AND with different angles and attacks from your fingers.