What is a hammer-on?
A hammer-on is basically when you play a note, without picking the string, on a higher fret.
How do you do it?
Fret the 12th fret on the 2nd string with your index finger. Done? Now, get your 2nd finger ready. Pick the string, and bring down your second finger with enough force on the 13th fret. If you do this properly, the 13th fret tone should replace the 12th fret tone, even though you did not pick it again. If you did not "hammer" your 2nd finger on the 13th fret right behind the fret, or with enough force, al that will happen is the first note will stop ringing. Try repeating the hammer-on, and keep repeating it, until the second note sounds out clearly, every time.
Hammer-ons help your playing be faster, as you do not need to pick. Try doing the pentatonic scale with this technique, it's really fun!
Tips
* If you do not get the second note to ring out clearly, make sure you are hammering right behind the fret.
* Repeat this technique on different strings, and on different frets. Each string is different to hammer on
* Try to hammer on two notes simultaneously. For example, pick the 12th fret, 2nd string, hammer on the 13th fret, and next the 14th fret.
Pull off
The pull-off is a technique that is the opposite of a hammer on.
How do you do a pull off?
Put your index finger on the 12th fret, 2nd string, and your 2nd finger on the 13th fret. Pick the string, take your finger off the string. As you do this, slowly pull down on the string. This will cause the fret your first finger is on to sound out .. You probably will not get it the first few times. Keep practicing the technique, and you'll always get the hang of it.
Once you've mastered the above mentioned guitar techniques, try to challenge yourself, by playing things that have both hammer-ons and pull-offs. One of the best (and most productive) ways to do this is to play scales. Hammer on when you're going down, and pull off when you're coming back up.
Additional stuff
* Hammer onto a note, then pull off immediately. See how long you can do this without picking. This is known as a "trill", and is used in many songs.
* It's very easy to give up when you try out this advanced technique. Keep practicing and you'll get the hang of it.
* Hammer ons and Pull offs are very popular in guitar, so it's vital that you master these techniques.