While I'm the last person to impose "rules" onto the making of a film, there are certain common elements that emerge when you examine the classics of this genre, elements that run mostly in the subtext and hence work on the subconscious mind. Working on the subconscious is essential to evoking an emotion that has evolved over millions of years and has been buried deep inside the psyche: fear. Once you take care of the subconscious, you can spread you creative wings to work on the conscious.
So, the common elements of horror classics:
1. Always, always set the scene of your story in an isolated place, not surrounded by any physical human interaction for many miles in all directions. The reason this is of paramount importance in evoking fear is because it evokes another emotion that in turn evokes fear: helplessness. If shit goes down, there's no one around to help. Humans have evolved in groups, always living and hunting and protecting in groups. The very presence of another human being in a lonely place, even if he's an unlikable character, can create a sense of comfort. That's the last thing you want in your film - comfort. Remember that while watching the film, every member of your audience places him/herself in the place of the protagonist, mentally detaching themselves from the asshole in the next seat. By placing your protagonist and/or his family in an isolated location, preferably geographically detached from civilization, you are also psychologically detaching your audience from everyone else. That sets in helplessness, the most delicious item in your recipe. Think of this as the no-escape rule. It's so powerful that even if you are cognizant of this plot tool, it STILL works on you. Additionally, it also serves an another purpose: at the climax of the film should you choose to return your protagonist back to civilization and restore normalcy, the sudden burst of relief you would aim to achieve in act III, the conclusion, would be amplified manifold.
Examples: The Shining - set in a hotel in an extremely isolated place that is literally cut off from civilization during winters. In fact, to establish the extent to which it is isolated, Kubrick opens the film, as the credits roll, with a bird's-eye view of a car driving to this hotel through long stretches of uninhabited mountains. Evil Dead - a cold, lonely place in the woods, connected to only by a bridge that our Evil Force rips apart early in the film. Psycho - a gigantic single house and motel set in the middle of nowhere, with no one to reach out to if nigga comes attackin'. Setting your film in such a lonely place does half the job of creating tension and terror. The audience may not consciously think about all of this, but it's ALWAYS there in the back of their minds that there is no one out there to help, that the VIEWER, not the protagonist mind you, is in a state of helplessness. That activates every fear and anxiety center in their brains. It doesn't matter if it is supernatural horror or natural horror, it works.
A bad example of this would be The Woman in Black. They do set the story in an isolated village, and the house of interest IS away from the village, but the very fact that there are PEOPLE in the village accessible at anytime to the protagonist takes away all of the anxiety and fear characteristics of the story.
2. Never show the ghost till the very climax of the film, at least not completely anyway. This one applies only to supernatural horror. What is not visible is always scarier than what is. There's a reason why we were afraid of something being under the bed in our childhood. We can't see it. We imagine it. As a filmmaker, your most potent tool is not any of your overpriced editing gadgets but the imaginative power of the mind of your audience. Don't work ON it, work WITH it. Show them glimpses, occasionally, if you must, but never the whole thing. However, keeping them completely ignorant about the ghost can work against you. There's point after which the audience tires out of imagining all by themselves without receiving any catalysts and cues. Reveal the whole thing only at the climactic end, and when you do reveal, make sure it rewards their feared expectations. Don't build so much tension during the course of the film and in the end "reward" them with a ghost that looks like a constipated cat. They'll hate you for it. But to some extent, this can be applied even to natural horror films. In Psycho, the mother (or what's left of her) is not shown till the very end of the film; but as a general, it's more applicable to supernatural horror since supernatural ghosts ignite the audience's imaginative creativity more than a familiar human figure.
3. Set MOST, not all, of the events in the film in the dark. The dark, as Kirk Douglas nailed it in The Bad and the Beautiful, has a life of its own. "In the dark," he continues, "all sorts of things come alive." There are again evolutionary bases for why dark in itself is pants-shitting scary. Having a fear of the dark because of there being some sort of evil ghost out there kept our human ancestors from venturing into the dark at night, thereby protecting them from predators in the jungle. Fear of ghosts, as modern science suggests, was instrumental in our species' evolution - not because ghosts exist but very the fear of it protected them more earthly predators and kept them from extinction. A mere fear of predators wasn't enough to protect them at night because dark essentially made them blind and gave the more evolved predators an evolutionary advantage. A fear of something more sinister, however, worked to their advantage. This fear was only necessary at nighttime, since if they stayed locked in their caves day and night out of fear of ghosts, they'd starve to death. Daylight gave them all the advantage they needed to hunt, and their fear gave them all the protection they needed at night. Fear of the dark is ingrained into our very DNA. Combine this with point #1 and you are almost done with the subconscious architecture of your film.
4. For fuck's sake, don't include gay people in your movie. You are making a horror film, not a Prada commercial. We unfortunately live in a time of political correctness gone mad. Don't have black people in a positive role? Get accused of racism by black organizations. Don't have women in intelligent roles? You such a sexist pig! Mildly pat a dog? Get sued by PETA. And lastly, don't have two men making out with their tongues in each other's mouths and in YOUR face? Homophobic! What happened to all the good old days when you could just make an honest film without being counterproductive to the film's emotions? Even gay people find gay people in horror films un-horrifying. Stick them to the chick flicks.
5. Stay away from loud noises. This is a direct result of advances in sound engineering. A silent scene, the protagonist looks around the room, the lo! The ghost pops out of nowhere and the speakers tear their anuses apart and bang your eardrums out. Almost every horror film being made these days abuses sound technology this way. But you don't. Instead, use atmosphere and mood to create fear. Create a consistent tone with creative use of lighting, camera angles and movements, solid performances, believable character reactions and their motivations. NOT through bullfucking aural rapefests at every turn you take. Watch old films of this genre, classics or not, because they could scare you without using cheap-ass sound effects.
This newly invented lost-and-found-footage genre horror has actually taken care of this problem. They obviously can't use sound effects since there's no score. [REC], the Spanish original, is a perfect example of a very well made modern horror film that scares through atmosphere and intelligent storytelling without the use of nuclear bombs for sound. Both sequels sucked, the American remake sucked harder, but the original still retains its shine.
6. Lastly but equally importantly, the film should be a progression, not stagnation or decline. Start the film with some tense event, if you so choose, since it's important to grab the audience's attention from the start. But from the next scene on, bring it down to almost no drama, no action, no excitement, and slowly build your way upward, clue by clue, event by event, until the climax where everything, or most of it, is revealed and dealt with. Paranormal Activity, for example, doesn't reveal too much the very first night he places the camera. Only the wind blows. The second night, well I don't remember exactly but something slightly more noticeable happens, and it builds on and on. This is the only way you can do it because giving away too much at the very beginning creates two hurdles: 1. The audience won't be able to take in too much info in too little time. You have to gradually slide it in, like a frog in a glass of water that is being slowly boiled without its being aware of it. 2. The audience will be disappointed when what follows isn't more exciting than what came so far. It creates stagnation and saturation and elicits that very familiar response: boring. [REC] actually does this building up of tension in such a clever way that starting at the ground floor of the building, the tension and excitement builds with each floor they go up, revealing more and adding more conflict, until they reach the penthouse where all hell breaks loose.
That's it. I could still add in a few more generic themes, but I've already bored you enough. Goodnight amigo, and stay straight!
