One hand at a time, play a phrase, or part of a phrase, very slowly. Using the printed finger numbers as guidelines, fill in the gaps with the implied fingering. Use your knowledge of scales and arpeggios to fill in the rest. Try it at the projected final tempo. If the fingering is still comfortable, proceed to step 2.
Add the notes directly before and after the part you’ve just fingered. Does your fingering fit with them? If not, make the necessary changes. If so, go to step 3.
Write the fingering in the music: write all numbers if the passage is complicated. Otherwise, write in guide numbers. In the scale and arpeggio passages, for example, the numbers that will help you most are 4, 3 and 1.
General principles to keep in mind
Establish a “permanent” fingering early on. Use it every time you play the passage and don’t change it unless you’re sure it doesn’t work.
If a passage is difficult to finger, find the spot that can only be done with one possible fingering, and work backward or forward from that spot.
Avoid using weak combinations, like 4-5, at important points.
When fingering repetitive patterns or sequences, try using the same fingering for each pattern. If keyboard geography makes any one pattern too awkward, change its fingering to fit, but don’t be afraid of using 1 or 5 on black keys.
If the printed fingering doesn’t work it can be changed. Have a good reason for changing it, though, and write your fingering in the music.
If you mis-finger something during practice, stop and write the fingering in the music immediately. If it’s already written in, circle or highlight it and drill immediately.
If mistakes keep occurring in a passage, search for a new “permanent” fingering.