Ok, I've got my alternate picking down to a reasonable speed. I can do a three octave scale in 16th notes at about 120bpm. I can pick really fast on one string but changing strings presents problems. I used to mainly use my wrist and elbow to move the pick, but today I realized that with some practice the thumb and index finger (fingers holding my pick) can also do the job. Which is better for speed? Also, are there any tips on gaining some phenomenal speed?

I would like to be able to shred in a way that makes people go "wow".