I believe that the ONLY method of practice that really works is to play each excercise (at ANY tempo)till you can play it 100% correctly. My clarinet teacher taught me that way and it works. Take a phrase that's difficult or new to you and play it at ANY tempo that you can get through it .... even if it's 5 BPM! It doesn't matter how fast at first, but get it right, or don;t move on. Once you DO get ot right .... start increasing the tempo till you get it up to the correct speed.

This follows that "perfect practice" technique that was mentioned earlier. Follow Billy Joel's advice - "Get it right the first time, that's the main thing"