When I was a floating bank teller in a previous life, I had a set of spiral-bound index cards that I wrote EVERY POSSIBLE computer code in.
That little book was kinda famous... I floated among 15 different branch offices in our part of the state, and it wasn't unusual for someone to track me down at a different branch just to ask for a code, because they knew I'd have my little book with me and that I could find it faster in my little book than anyone else would be able to find it in the Branch Operations Manuals.
Index cards are hardier than just note paper and better able to stand up to lots of thumbing-through. You can also get tiny two-ring binders for index cards and make your own sets. With the ring binders, you can change out cards, insert tab dividers, rearrange the order of your cards, etc., as needed.