Originally Posted by: RiskyNZ
Method Two: Constantly bump up the metronome past your limit and keep reaching for higher speeds.

The other posts above pretty much hit, I would only add with the above emphasis changed to pushing your limit. Always be sure, as the others said, that you are plying it the right way. If it is a faster riff you seek to play, you do want to practice your way to getting up to speed. First, get it nailed at a slower speed, then move to the next 'speed step' and continue to bang it out until you can play it at a new speed comfortably and correct and move up.

You do have to push upwards but never really past your limit.