Watch the Percussion Introduction online guitar lesson by Peppino D'Agostino from Acoustic Poetica: Fingerstyle Etudes
At the very beginning of this etude, we're already in A minor position and the very first percussion (shown with X letters) is done with the tip of your index, middle, and ring finger landing on the 4th, 3rd, and 2nd string, creating a sound reminiscent of maracas. Immediately after the percussion, you pluck the 4th, 3rd, and 2nd string playing the A minor chord.
The 2nd percussion (2nd beat, 3rd sixteenths) is done with the index finger landing on the 5th string. It's important to land exactly on the 5th string because the next note is an open A note. On the 2nd beat of measure 3, please note that the C note is played simultaneously with a percussion of your index and middle finger on the 4th and 3rd string. On the 7th measure, please note that the F on the 6th string is played with the thumb.