chomatic patterns are excellent as well three note per string exersises as stated above. Make sure you are putting some logic to these. An invaluable tool for this is and always will be the metronome. I dont know one guitarist who got blazing fast and incredibly accurate without using one. Make up nonsense patterns and set your metronome to a sensible beat to start with. Play sixteenth notes, triplets, and sixteenth note triplets making sure you....#1 cover all parts of the fretboard and #2 making sure you always accent the note that falls on the beat. I cant stress how important the stressing of that note is. Its a great technique for developing control. anyone can play fast but most lack great control. Most people wont use a metronome because they know they will be humbled. If you are serious about your playing, then go buy one. Picking is also dependent on both hands being in shape. I wont go into this but i'll refer you to a video that expands upon what i have talked about above. Its john petruccis rock discipline. Its without a doubt the best teaching tool for the guitar to ever be created. If it wasnt for that video (4 yrs ago), I'd still have problems playing "mary had a little lamb". If nothing else, you'll get to see john put Vai to shame by playing chomatic sixteenth note patterns at a jaw dropping tempo of 208 beats per minute and flawlessly at that. Hes quite possibly the most accurate and fastest guitarist to ever walk the planet (sorry vai).