Sorry for the late reply XD
just as ambinate posted, its basicly a harmonic trick, its the easiest to do on the 5th fret G or high E, its a very light tap on the string like joe satch does it, and when/if you get the harmonic, trem/whammy it up down, shake the guitar if you have no trem arm () etc....., you can even do it near the pick ups, i think the youtube video explains it better.