Minimum movement of both hands (and the whole body) is a good step. Keep your fingers within a sixteenth of a inch from the strings, and play scales as slowly as you need to to keep the beat steady.
Develop the pinky on the fretting hand: Pinky, ring, pinky, middle, pinky, first, pinky, middle, pinky, ring, etc. Start by staying on the sixth string: 4th, 3rd, 4th, 2nd, 4th, 1st, 4th, 2nd, 4th, 3rd frets... with minimum movement, of course...
Play any note with a death grip, and repeat to the beat. Slowly relax the grip until the note is just getting a little muted. Play it with this tone as long as you can. Slowly vary the tone by SLIGHTLY pressing harder or slightly backing off the fretting hand. Realize you'll never have to press harder than the minimum it takes to get good tone. Every extra bit of pressure steals speed AND expression (Kind of nasty to choke an instrument, isn't it?).
Do similar things with the picking hand.
Massage and stretch your hands and fore-arms before, during, after, and between sessions.
Extreme speed and extreme slowness can be very lovely.