As I mentioned in an earlier article, you should practice little but often, because it is far better than doing long periods of time at once. As far as an ideal practice session? It will vary according to your level, but ideally, you’ll get to a point where you will always start with your technical exercises. About a quarter of your total practice time should be spent on these exercises. Upon completion of the exercises, strive to work on three pieces at a time. Although this is difficult and it takes tremendous discipline to pay equal attention to all three pieces, it is far better than working on only one. The best way to work on a piece is by choosing a section (such as one line), then work each hand separately in multiples of three until the line is at least 80 percent fluent. Then begin putting it together, but as you encounter particularly difficult areas, go back and do it separately again and repeat the process.
Difficult passages need to be played over and over until they are correct. Who’s to say how many times that may be? Sometimes 30, 50, 100 or more play-throughs may be necessary to get that part right. You must be patient. It could be that just one more pass will allow it to “click” for you. You must also make sight reading part of your regular practice. Every day, look at one line of a piece of music that you’ve never seen before and study it for 30 seconds. Then go ahead and play through, trying to get it perfect on the first pass. If you make mistakes, that’s fine, but don’t go back and play it again, because it is no longer sight reading. The practice session that I’ve just described could take at least half an hour and probably more, but you can tailor it to shorter sessions if necessary.