Twenty five years ago while living in Santa Fe, an elderly pianist shared this practice technique with me. She said that is was a method used by Mozart and had been passed on to her many years before.
Use this method to perfect problem areas in pieces you are working on.
First define the exact cause of the problem. This is something usually quite small. Now correct the small problem. For example it might be a better fingering etc.
If you cannot figure out what is causing the problem or you are unclear on how to correct it, then you need a good teacher. So find one....
After you have an absolutely clear idea of what the solution is, you are ready to use the following method.

Take ten match-sticks and place them on a table next to you. Mark the problem area in pencil. Set your metronome at a very slow speed so that you can get through the problem area slowly and perfectly. Start playing a few notes before the problem area and finish playing a few notes after it. It is important to play into, through, and out of the problem area correctly. When you have done this move one match over.
Now repeat the process again playing the section 100% correctly and move another match-stick over. Continue repeating the process. If you make a single mistake such as missing a note, getting a buzz, breaking the rhythm, using the wrong fingering, etc. push all the match-sticks back and start again at number one.
If you make a mistake on the tenth time you must start again at one. If you cheat you only hurt yourself.
The match-stick method of practice is very effective. When used correctly it does the following:
It is a great tool for focusing your mind. There is a clear and concise short term goal to concentrate on which is playing the problem area correctly. As you move match-sticks over you become more focused and concentrate because you don't want to make a mistake and start over again.
The match-stick method practiced correctly yields consistency. You have taken a problem, corrected it and are now able to play it perfectly at least ten times in a row. That's an accomplishment.
This method takes a problem and uses it to make you a better player.

So that's it! A simple technique which will yield excellent results. Technique serves the music so as you use this method do it as musically as possible.