I am given to understand that one of the (very few) differences between the big cats and the small cats is that the small cats (not all of which are small) can tuck their paws in, while the big cats can’t.
In the order they were in when you took them out of the boxes and stuffed them into the bookcase after you moved. I don’t bother with a system. I just remember roughly where each one is. Yes, I can remember the locations of a couple of hundred books. I can remember the locations of a few hundred books in the Barr-Smith library in 1967. I can remember the locations of a few books in the Stockholm public library when I popped in for about half an hour in 1975. I can’t remember what my wife asked me to get from the shops today.
They twist themselves into the most unlikely positions, and yet seem comfortable.