Pull-offs are performed by picking the 1st note and "pulling-off"
to sound the 2nd note without picking it. Both fingers
are to be placed on the notes to be sounded. Strike the
1st (higher) note, then sound the lower note by pulling
the finger off the higher note while keeping the lower
note fretted. It's hard to get it to sound right at first,
but keep practicing.
In tablature a pull-off is represented by a "P"
and a curved line connecting the two notes like in the
example below:
Here are some more advanced pull-offs to practice. They're
a little tough at first, but as with everything else,
it's nothing practice won't cure.
The previous two examples are built off of the pentatonic
scale. You can learn more about the pentatonic scale in
the scales section of the Guitar
Alliance Members Only site.