Fast is no big mystery. It is actually the easiest part. When you learn the tune, look at what you are doing CAREFULLY. Check out the pattern that you are making. Is it the most efficient? Is it aesthetically appealing?(I play better with pretty patterns) And, after you have it down, play with someone who is ever so slightly faster than you are with that tune. Fast is easy. Accuracy, now thats the one that takes LOADS of pracatice.