With a metronomer, practice at slow speed, too slow, about 50 bpm.

Then increase a little bit to 55 bpm, then to 60, and so on, until you reach the original bpm of the piece or exercise. Sometimes i like to pass the original bpm, because if i can play at a faster speed, it will be more easy to play at the original tempo.

Man, don´t be hurry. All the notes must sound clear, all the techniques must be executed with perfection. And only after this you must go to the next level and increase the bpm.

Remember, to play well, you don´t need to play fast. Some of the best pieces of all the times are at slow tempos.

Hope this can help you. See ya!