I also did what Stacia recommend:
I marked all my Fiction with genre stickers: Historical Fiction, Mystery, Science Fiction, Fantasy, Realistic Fiction, Humor and Romance.
Anything Visual helps: For example, all my Fiction shelves (FIC, PB FIC and Multiples copies) are marked with big letters (Black on red paper) so students will find the section of the author they are looking for. I divided the Manga in Shojo and Shonen genre. I put then on top of my lower shelves on wooden racks that were made by student as a wood working project...