Poll: How do you organize your DVD movies collection?

What is your main criterion when it comes to organize your DVD movies collection? Discuss here PS: these criteria can overlap one or another, like it's possible to rank the movies by director and rank the directors alphabetically by name (Altman, Bertolucci, Chaplin...) or first name (Akira Kurosawa, Brian de Palma, Clint Eatwood) but the main parameter will remain the director.