Genre, using broad categories (e.g., Mysteries, Technology, Jazz, etc.).
Alpha order, by first name of artist/title/author.
A colored dot, to denote the genre (e.g., red dot is mystery book).
With this system, when you need to put something back where it goes, it’s obvious where to start. When your system is logical, other people can also find something when they need it.
Have you created a system for organizing these items? If so, leave your tips in a comment.