Here we have a fast sixteenth note riff. The chords are hit on the downstroke with the open A string pedal alternate picked. For the legato fill in bar 2, you will need to be accurate and almost snap back into position for the following chord. For this reason I would advise using the fretting hand fingers 1 and 4, to play the A powerchord.
For the pinch harmonic, slice down lightly with the pick at a 45 degree forwards angle and follow through gently with the side of the thumb. The key to getting a cool pinch harmonic sound is the vibrato that follows, so once you have it, apply wide vibrato by pulling downwards a whole tone and back three times.