This exercise is a fundamental technique builder for finger strength and independence. Played slowly, it is an ideal warm-up since it uses all of the fingers of your left hand. Ascending through the pattern, add fingers (one per fret) playing each note until all four fingers are holding the string. Then, WITHOUT LIFTING your second, third and fourth fingers, move your first finger to the next (3rd.) string and play that note. Next, move your second finger to the next string and play that note (again, note moving any other fingers). Once all four fingers are placed on that string, continue on to the next string and so on, until you reach the first string.
When descending through the pattern, place all four fingers on the first string and play the note under your fourth finger. Lift that finger, then, play the note under your third. Continue until only your first finger rests on the string. Repeat the process until you run out of strings. You have two choices of what to do with your fingers that aren't resting on the string. One, hold that finger as close to the string as possible without touching it. Or, two, place that finger on the next string much the same way as you did when ascending through the pattern. This option feels weird because you won't be playing the note under the finger that moved to another position on the fingerboard. The best option is to practice both.
Things to keep in mind:
1) PLAY SLOWLY.
2) Pay attention to every note and make sure it isn't muted by another finger.
3) RELAX your hands as much as possible. This exercise is impossible without completely relaxed hands.
4) Practice using alternate fingering between the first and second fingers of your right hand until your a completely comfortable with it. Pay particular attention to developing perfectly even volume and note placement.