My bound reference was very (overly?) structured; I started at the front of the book with things I forgot about often - different probability rules, geometry stuff, index/log laws, odd/even functions, stuff like that. Wasn't just a list of rules, but also included a few diagrams. Basically it was what my summary would be if it could only be one page. After that was calculator syntax; for the useful TI default ones that I didn't use much (angle, stat calcs, etc.), and programs I'd written on my own so I didn't accidentally put things in wrong.
The bulk of my bound reference went like this, where a topic was a collection of chapters (1-7 in Cambridge methods being 'functions', etc.):
- Summary of whole topic at a glance.
- Checklist of mistakes not to make by topic. (e.g. remembering to write the inverse as f-1 and not y.)
- Chapter X Theory
- Chapter X Examples
- Maybe a chapter summary if it's particularly long
- So on and so forth until the end of the section
At the very back was anything important that didn't fit other places, and between the end of the section notes and that was anything else; usually worked solutions from SACs and practice exams.
I wouldn't recommend my approach to everyone (anyone?

) because it was a lot of work; got $20 out of in the end when I sold it but otherwise it was pretty much worthless because I didn't touch it during the exam. You could argue that because I made it so meticulously I didn't need to check, but in any case I didn't get any use out of it.
I found that of my friends who used their references, it was generally those who were neat and organised that got the most out of them - colour coding, tabs, etc. . Personally I believe that the bound reference is a bit of a waste of time in an exam because it takes away from value working time, but it also could save you marks if you forget. I would recommend a 'lighter' approach; listing rules and how to use them. Anything else is a waste of time - both in an exam or sac when you have to flip through the fluff to find what you're looking for, and in the time that it takes to write it out anyway. ofc in the end, it's up to you; do what you feel comfortable with, and if you're not sure, do more.
