This is also know as a "scream", it is a high pitched noise made by placing the thumb infront of the finger that is plucking.
In more detail about an inch and a half behind your thumb is the other finger. Put your thumb parallel to the pickups, so that the side of your nail touches the strings. Try it with an open string. You most likely will not get it first try but try on different parts of the strings, you may well find things I like to call "sweetspots" where it is easiest to strike the harmonic. On my strat they are in between the pickups.
Once you have mastered the open string try doing it with some notes, it will be a bit more difficult. The easiest string to strike it on would be your low e, the harder one being a high E.
Note: This was my first lesson, any help/critisism would be helpful. if you found this lesson unhelpful pm me and tell me how I could improve.
