Find the gaps in your knowledge, any subject
For example with GCSE Maths
Find an alphabetic glossary of terminology.
Create two sets of these alpha notes page by page
One in alpha order
One in specification order
Use the same file possibly, with one easily located and identifiable halfway divider for the two sets alpha and specification and then a range of colour dividers for the spec module set.
Read the modular and check school notes. Create missing ones, check you know all the alpha glossary terms and can work out examples.
Add past paper Q with the same colour code?