End credits can also be dictated by the studio. I was sent a template by the higher ups that they follow on every picture, to be filled out in that order. I think it started with the ADs and then went through the various departments (camera, sound, production, hair, makeup, wardrobe, grip, electric, transpo).
Like Derek said, if names aren't mentioned in the opening credits then you usually start with Directed by and then the cast list, then crew.