The Horror of Film Making

Horror is frequently celebrated as the movie genre that young, inexperienced filmmakers can start out with but horror is much more complicated than that, and scaring an audience that's becoming more and more desensitized to gore and violence means we as filmmakers have to do our homework. The right atmosphere is an incredibly important part of any horror film. Bad actors, bad audio, or a story full of holes can potentially be made up for with a solid mood. 
Filmmaker Magazine says:

"A good horror film has an underlying atmosphere, a moody visual undertone that creates a sense of dread, wonder and mystique and leaves us with snapshots of unforgettable imagery. This is well exemplified by foreign-language films like The Devil’s Backbone, The Orphanage, and Tale of Two Sisters (the original Korean version). These films rely more on isolation — both literally (through creative use of location) and figuratively (in the mind of the characters) — coupled with evocative cinematography and production design."

Another way to make your horror story amazing is mastering the art of suspense. Through the use of POV, camera angles, and the "MacGuffin" an audience can be forced to look through the eyes of the victim, or even the killer. Good foley work, ominous lighting, suspenseful music, or the concept of a "jump scare" (a loud or sudden bang or a flash of light) allow for maximum scare factor in any production.