For my textbooks, I use little record cards. I write the book reference on the top line, then whatever notes or quotations etc. If it's a heavily referred to book, I sometimes use different colour cards to mean different things.

When I return the book to the library etc., I take all my record cards out and put them in a little perspex index box.

Sometimes I use the record cards to then start some more detailed notes in a notebook; sometimes the record cards refer to a page in my notebooks where I've attempted a derivation etc.