For 'Full Access subscribers' there's a video lesson in palm muting here:


http://guitartricks.com/lesson.php?input=9624

Covering:

Guitar palm muting is done using the right hand. (picking hand) Basically what you want to do is slightly muffle the strings while you're picking the strings at the same time. To do this technique properly you'll want to slightly mute the notes you're hitting with your pick, but not so much that you can't hear them. The best position for your right hand is close to, or even directly over the bridge of the guitar. You'll need to practice various pressures until you find the right one . This technique usually sounds best with power chords and distortion

The first video shows the basics of palm muting. The second video shows palm muting with power chords and distortion.