If wat you wanna learn is the finger tapping or Fretboard tapping technique, here is some info.
Finger tapping is playing hammer-ons and pull-offs (trills) with your freting hand; while using the index finger of your picking hand to "tap" other notes.
Eddie Van Halen is known for using this technique, in fact I saw a video where they said that Eddie was the one who invented this technique.
There are a few examples you can hear in the Home page of Guitar tricks under the "by inspiration" menu. click on Eddie Van Halen.http://www.guitartricks.com/freelesson.php?input=bD5hOjVmZDY=

Another aproach to this technique is using the side of the pick instead of your index finger. And you can also add some slides to it (tap slide); sounds really cool.
Note: when you tap meke sure you press the string all the way against the fretboard.