HOW TO UTILIZE:
It may be a simple little lick, but you'll be amazed at how much information and how many ideas we can derive from "Breakdown". The song is in the key of A minor, and the riff is based the A minor pentatonic scale.
Although, as with almost anything on the guitar, you can play this riff in several different places on the neck, we're going to play it up around the 12th fret. Try playing the A minor pentatonic scale (seen below) starting at the 12th fret. You'll notice that the scale doesn't actually start on the note "A" when played in this position. The root for this scale position of the minor pentatonic is the first note you play on the fifth string. If you wanted to play a Dminor pentatonic scale using this shape, you'd start it on the fifth fret of the sixth string (so the first note you'd play on the fifth string would be "D".) Try and get comfortable playing in this different position - it's unhealthy for a guitarist to get stuck in the same old "root-on-sixth-string pentatonic scale".
What makes this lick so interesting is it's use of sliding, to create a sort of slippery effect. Practice playing the scale, picking the first note, and sliding to the next note on that string. Then, try hitting the first note, sliding to the second, and sliding back to the first, all without re-picking. Try the same technique to different scales you know. Experiment, and see if you can't come up with different combinations of notes and slides that sound good to you. Then, try incorporating bends, hammer-ons, and slides to your riffs. Try playing a familiar song riff you know using slides or bends to play notes you'd normally re-pick. Concentrate on creating your own riffs, using the ideas presented to us in "Breakdown".