I use 3 sizes of post-its, the index card size, the square ones and the small square versions.

I have put a few of these each into my moleskines. On the backpages where there’s also the address booklet/foldout flap, you can stick the index card size to the address booklet’s cover. On the opposite side i have put the square ones and above these snuggly fit two times the smaller ones….

I use the square ones for smaller daily to do lists that i can easily stick on the outside of my moleskine with the non-sticky side facing the elastic binder, so it wont come off…

The indexcard size is good for bigger notes etc while the smallest are good for handing out contact details etc.