Practice trilling with your ring and pinky fingers (especially that pinky). I find that in my playing I use my index finger and pinky finger in almost everything I play. The ring and middle fingers only get about half the action that my index and pinky get.
Trilling - Only pick the first note. The rest are hammer-ons and pull-offs. Try to keep it up for 30 seconds at first, then a minute, then two, and so forth. Great thing to do while talking on the phone or watching tv.
index and pinky
|5-8-5-8-5-8-5-8-5-8-5-8-5-8-5-8-5-8-5-8-|
index and ring
|5-7-5-7-5-7-5-7-5-7-5-7-5-7-5-7-5-7-5-7-|
index and middle
|5-6-5-6-5-6-5-6-5-6-5-6-5-6-5-6-5-6-5-6-|
middle and ring (this one is hard to do at first)
|6-7-6-7-6-7-6-7-6-7-6-7-6-7-6-7-6-7-6-7-|
ring and pinky (this one's hard too)
|7-8-7-8-7-8-7-8-7-8-7-8-7-8-7-8-7-8-7-8-|
"You must stab him in the heart with the Bone Saber of Zumacalis... well, you could stab him in the head or the lungs, too... and the saber, it probably doesn't have to be bone, just anything sharp lying around the house... you could poke him with a pillow and kill him."
- Aqua Teen Hunger Force, The Universal Re-Monster