Pick Harmonics

This technique is fairly tricky to master. To accomplish it you must strike the string with your pick and your thumb at the same time.

The trick here is to expose a very small portion of the tip of your pick (approx. 1/16" or so), so that your thumb will always just barely touch the string as you pick it. When you get it right you'll hear a high pitched whistling sound which is the harmonic of that note.

Try above example.