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.