1. First, pick a note. Any note. Fret it on your guitar, preferably with your pinky finger.
  2. Think of the pitch you want to bend up to. For starters, go for one half step (one fret) up. Play that note now, and have it in your head.
  3. Put down your other three fingers on the string behind your pinky so that they're touching each other.
  4. Pick the string, then push all four fingers simulateously down towards the fretboard and up towards your nose (be sure the string moves along with them, and stays fretted so that the note continues to sound). You should hear the pitch rise.
  5. Congratulations! That's a bend! By physically bending the string from a straight line into an angle, you've put more tension on the string, and thus raised the pitch.
  6. Stop bending when you think you're one half-step higher than you were (or whatever interval you were going for). Hold the bend for as long as you like, then allow the string to return to its original position, keeping pressure on it all the time so that it stays fretted and sounding. This is caled the release. If you just let go at the top of the bend, you get a very wicked-sounding pull off.
  7. YMMV depending on your skill, the weight of your strings (lighter strings make bends easier), the number of fingers you can put onto the bend, and other factors, but I can bend at least 1.5 steps up from the original note in this manner.
  8. You can practice this by playing a note, then playing the note above it (usually a half step or a whole step higher). Sing the higher pitch in your head, then play the first note and bend up to the note above it until you're matching the pitch in your head. Go up and down a scale this way. Incorporate this into your daily practice routine (you do have a practice routine made up for yourself, don't you??) and you'll get very accurate with hitting the pitch you want, and not over- or under-shooting.