One of the most popular techniques associated with Hard Rock and Metal guitar playing is right hand tapping. This involves the use of hammer-ons and pull-offs on the fretboard with either the index or middle finger of the right hand. To begin with, try a single tap by hammering-on to the 12th fret of the 3rd string.
Once you can sound notes clearly and evenly by tapping on the fretboard, the next step is to tap a note and then pull-off immediately after tapping the note. In the following example, the left hand holds a B note at the 4th fret, 3rd string while the right hand middle finger taps the 12th fret (a G note) and then pulls off immediately to sound the note held with the left hand. Listen to the CD to hear the effect of this technique. A tap is indicated by the letter T above the tablature. Remember that the pull-offs here are all played with the right hand.
When you can easily play the previous example, try this one which moves up and down the 3rd string a bit more.