You can section up the works into its parts, I usually put A, B, C, Ai, Aii etc in little boxes. Showing shape of the passage in terms of the black and white notes, eg CEbG is a triangle shape, can also show hand positions in this manner too, or larger scale passages. Include memory hooks and patterns found in fingerings, like perhaps certain fingers come together, certain fingers replace the other, or perhaps focus on similar notes in both hands or the subtle differences or how they theoretically connect in terms of chords, scales etc. Logical statements which help you memorize a passage. Movement groups, when the hand holds a position and when it has to move, can be done with brackets. Chords and scale labels, perhaps the scale starts on a particular note, or stops at a particular note, or turns within a particular part etc. Some students of mine who are learning to read find it challenging to notice when certain things come together or are inbetween so we will put lines connecting the notes to show togetherness and arrows to show inbetweenness. I think lots of color is nice, looking at black and white is so dreary, you can highlight repeated patterns within musical parts in the same color. You can also highlight which instrument the piano is trying to emulate to aid in expression ideas. And so on so on, lots to add on sheets as required.