Ironically enough, one of the answers to getting fast is go slow. If you can't play something slow, you'll never be able to play it fast. If you play something 100 times correctly at a slow and easy tempo, there's no reason why the 101st time should be wrong, where as if you're playing the same thing 100 times poorly at 200 bpm, then why would that 101st time be expected to be right? Like Jolly said, practice, but a metronome and slowing things down do help (I had asked about building speed already and the metronome thing does work...a lot).