Score study, or studying the sheet music, is a useful way to practice music away from your instrument. Here are some tips on how to practice using scorestudy. Things to take note of:

time signature changes
key signature changes
hand position changes
the overall form (more on this later)
tricky rhythms
chords (especially) cadences
patterns
dynamics
expression markings

Mark anything that you need to pay special attention to. Depending on your learning style, you may want to colour-code these, or make up some short code.

With regards to form, beginner students can look for repeating patterns. Intermediate and advanced students can label the sections as they know them (e.g. A section, B section, Exposition, Development, Theme 1, etc.).

I find it especially helpful to tap and count tricky rhythms away from any of my music instruments. Slowly and then gradually building in speed.

If you need more tips on how to scorestudy, don't be afraid to ask your music teacher.