Warm up your fingers in preparation to play by playing the chromatic scale on each string. The chromatic scale is simply the succession of notes on each string, played on each fret. Assign one finger one fret to play; for example, the index finger covers the first fret, the middle finger over the second, the ring finger over the third and the pinkie over the fourth. Count to yourself as you play (1, 2, 3, 4, 1, 2 and so on) up the neck.
Start your metronome, setting it to 60 beats per minute (BPMs). This is the same rhythm you used when you warmed up to the chromatic scale. Once you feel comfortable playing this beat, reset your metronome to a higher setting, such 80 BPMs. Continue to play the chromatic scale, but concentrate on your alternating (up and down) picking: A down stroke is one note, the up stroke plays the next and so on.
Continue to play. Once you're comfortable with 80 BPMs (or whichever setting you dialed in), set the metronome higher again, such as 100 BPMs. Experiment with playing other scales, such as the major and minor scales, to train your fingers to cover other strings on the fret board. The key to playing faster is repetition, so set aside practice time every day and start slowly. You'll build up speed, dexterity and strength through constant practice.