The most technically-challenging aspect of these examples is undoubtedly the fast alternate picking that crops up fairly often in the rockier examples, like Buckethead, Vivian Campbell or Gary Moore. Though each has their own approach to this, a few guidelines always stand true. To develop accuracy, you must have a clear plan about exactly what notes you wish to fret and synchronise this with your down and upstrokes with the pick. Starting slowly and using a metronome or drum machine as a timing reference is 100 percent more effective than just tapping your foot, which is way too forgiving. I know I’ve said it once, but let me reiterate: start slowly, with no concerns of speed! Take care of posture, minimum movement etc, and the speed will follow on automatically.