This is my usual method of practicing, gleaned from my teacher, old posts on the Piano Street forums, Graham Fitch’s Practising the Piano, and various other books and resources. It’s rare that I follow these steps exactly, but they are an ideal to aim for.
- Choose one section of the piece to practice, which is short enough that you can memorize it in a few tries. If you can’t, break it down into even smaller pieces. If it’s too easy to memorize, choose a bigger section. Include the first notes of the following section to make joining sections easier later on. For example, if your section is the first two bars of the piece, include the first note from bar three.
- Practice the section slowly enough, at first, to avoid making mistakes. If you keep making mistakes when practicing then you are just going to get good at making them, so it’s best to avoid them in the first place. Use the correct fingering, dynamics, articulation, etc. from the very beginning; you are never going to get around to “fixing” it later. Do not work on this section for more than twenty minutes.
- Start hands separately at a slow tempo using the metronome. If you can play the section five times in a row without hesitating or making a mistake, increase the tempo and practice again, until you can play at that tempo five times in a row. When one hand is in danger of getting tired, switch to practicing the other one. Aim to increase the speed to above the target performance tempo, so that playing at performance tempo is easier by comparison.
- Once you can play each hand individually above the target tempo, practice hands together. Start with a tempo even slower than you think you need—if you are having trouble coordinating, reduce the speed. Once you can play it flawlessly and without hesitation at least five times in a row, start increasing the speed in increments. Aim to get to a speed above the target performance tempo.
- Once you can play the section hands together above the target performance tempo, continue practicing it until you can’t get it wrong—but no longer than the twenty-minute limit. Some sections will take much less than twenty minutes to master. Others will take more, which is a sign that the section you’ve chosen is too big and should be broken down further.
- Start working on a different section, either of the same piece or a different piece, and don’t touch this section again until the next day. The next day, if you can play the section perfectly in only a few tries, move on to learning a different section. If not, repeat the steps above again. It will take less time the second time around.
- Once two consecutive sections have been mastered, work on joining them together as a new section. By adding the first note of the next section during practice, it is much easier to join sections together at this step.
- Continue in this way, working on small sections and joining them together, until the entire piece is learned.
While increasing the tempo, you may reach a point where you can’t play any faster, no matter how hard you try. What is likely happening is that the hand motions you are using—which come naturally at the slower tempo you started with—simply will not work at such high speeds. You are basically trying to run by speed-walking faster and faster. One way to get around this is to try playing the section at full speed first, ignoring mistakes, just to figure out what the necessary motions feel like. Then, you can try to practice those motions at a slow speed, not the motions that are intuitive at a slow speed.
It is a good idea to occasionally play a piece very slowly, even after you’ve mastered it. If you only play the piece fast, the piece will deteriorate as mistakes inevitably get introduced and never get fixed. Finally, it’s a good idea to occasionally play hands separately, especially for counterpoint, even after you’ve mastered the piece. In fact, for counterpoint it’s a good idea to learn each voice individually with the correct fingering (even if that means passing the voice back and forth between the hands) and occasionally play each voice separately.