Horror movies are a genre with many different sub genres, all of which are fairly unpleasant to find yourself as the protagonist in ...
The genre began in ancient Egypt, when a bunch of people said to themselves "Hey, those mummified corpses we keep around everywhere are actually kind of creepy," and performed a play about them coming to life and killing ancient Egyptian teenagers.
Unfortunately, the performers were then put to death for blasphemy, and the horror movie genre went underground until the beginning of the 20th Century. Since then it has diversified into many different subgenres. The popularity of these subgenres often reflects contemporary issues in society (see The Real World Fears Behind 8 Popular Movie Monsters.)
Popular types of horror movies today include slashers, vampire and zombie movies.
Movies in the 'pure' horror subgenre are often known as slasher movies. (This is not to be confused with slash movies, although sometimes the two are combined. For more information, see The Five Most Unintentionally Gay Horror Movies). Slasher movies, and to a lesser extent all horror, are usually made up of the following elements:
Boobs are horror's most important ingredient. Since horror is one of the few genres that appeals equally to both sexes, you might want to put in some shirtless males as well, but boobs are the real essential. (If your horror movie is over 30 years old, you might have to limit yourself to heavy cleavage and diaphanous gowns.) Basically, if you don't have boobs in your horror movie, you are obviously trying to be 'serious' and make some sort of important social commentary. This is wrong, and you should stick to making movies about miserable middle-aged men in suburbia or something.
Above: Boobs. Note the presence of Linnea Quigley (top), whose boobs appear in 43% of all horror movies.
It is best if you don't bother trying to think of clever excuses to have boobs in the movie. Return of the Living Dead, rated the best horror movie of all time by an astonishing one hundred percent of horror fans*, simply inserts a strip scene in the middle of the film, and the chick never puts her clothes back on. (For more details, see Great Moments in Gratuitous Sci-Fi Nudity.) This is probably the way to go.
*sample size: 2
Death and Violence
You should probably make sure your horror movie has some violence as well, or it will actually just be soft-core porn. Watch out for that. The level of violence is variable, but as a general rule, pretty much everyone in the movie must meet certain death.
The type of violence is also variable. A slasher will offer a wider variety of deaths (stabbing, drowning, burning, etc) than a zombie movie, where most people will simply be eaten.
A particular set of characters are essential. They are:
The Boyfriend/Other Male Characters
We're sorry, but you are in a slasher film and you have a penis, you are going to die. In fact, you are probably going to die first. Being the first death, you will probably die in a particularly slow, gruesome way. You may as well just shoot yourself now. It will be quicker.
Good news for you 3% of Cracked readers! If you're a girl, you have a minor chance of surviving. Unfortunately, you can never ever have sex. If you do, you will die. At least it might be quicker than the poor dude who died first, but you will probably have to run around tripping over a lot before you die.
The Final Girl
You can claim the place of the final girl and survive a horror movie if you never ever have sex or show your boobs. Since a lot of boob scenes in horror movies take place in the shower, this might entail bathing fully clothed for the rest of your life. When your clothes eventually rot off, make sure you have some new ones at hand before we accidentally see some cleavage or something.
Some movies bend the character rules, either by killing off all the characters (presumably all of the females in the movies were either non-virgins, or had showered naked at some point), or by leaving a final couple consisting of a male and female (these two are usually brother and sister, probably because the writers figure they are unlikely to ever have sex.)
A sole male final survivor was rumored to exist in the 80's, but there is no way you could be as awesome as him, so don't even try.
Stop quoting him, as well. You can't do it right.
Horror movies inevitably start off with a bunch of happy, normal, attractive people with lots of friends. Horror movie fans see this and feel anxious, as they are being confronted with visual confirmation that there are people out there that do not in fact live in their own filth.
This tension is pleasurably released when the happy people all die in horrible ways, after watching each other die first. This makes the horror fans feel better. Sure, they might be 45-year-old virgins whose mothers are nagging them to move out of the basement, but at least they didn't just get stabbed to death after finding their secret crush impaled on the sharpened femur of their best friend.
Horror movies usually follow a pretty standard system of morality. Characters that break the code will die in a particularly awful way. Breaking the code can include betraying their friends, running away when others need them, picking on the virgin character for being a virgin, or simply acting like a douche to either the good guys or the villians.
If a character is a good person and doesn't betray his or her friends or act like a douche, they will probably still die, but chances are it will be quicker, and the audience won't laugh quite so hard.
The location of a horror movie is important. A typical setting somewhere out in the country, where horror writers and directors can express their guilt about their privileged backgrounds by making their characters get raped and eaten by deformed rednecks.
This place looks great! Let's split up and look around!
Suburbia is also a common setting, but only on the condition that none of the characters own mobile phones or any kind of defensive weapons, and that they all set up their bathrooms in advance so that the shower curtain is menacingly drawn closed.
For more information on locations, see 5 Vacation Planning Tips (According To Horror Movies.)
The slasher villian is typically human, but with unnatural strength/lack of death. This lack of death is compounded by his or her victims, who after seeing the monster rise again and again after being stabbed/shot/burned/impaled/drowned/burnt/tricked into non-existence/eaten by wolves/pushed into a woodchipper/covered with liquid nitrogen and shattered/ejected into space, still turn their backs on the guy right after they kill him, when they clearly should be nuking him from orbit.
Not that that would help, probably. But it might look cool.
For examples of people that have got this part wrong, see The 5 Most Half-Assed Monsters in Movie History.
This deals with vampires, zombies, ghosts, werewolves or some other mythical creature. The particular type of monster shown in a movie tends to rise and fall in popularity. In the last decade, zombies have been popular, but vampires may just be making a resurgence.
For more information, see 5 Scientific Reasons a Zombie Apocalypse Could Actually Happen .
This is for directors who want to make horror movies, but whose sociopathy unfortunately prevents them from understanding basic human emotions or characterizations. Plot, characters and expensive set pieces are unnecessary, as all you need is some dude strapped to a chair for 90 minutes while people cut his fingers off or something. This movie is then called 'edgy'.
People are usually afraid to criticize the bad taste or the lack of plot or characters in these movies for fear of their friends finding out that they are not 'edgy' enough. This makes sense, since only total squares are put off by prolonged, realistic portrayals of innocent people being tortured to death.
In recent years, America ran out of ideas and eventually turned to the Japanese. Finding their horror movies to be surprisingly lacking in robots or bizarre sex, we started first importing them and then remaking them in ways that usually completely miss the point.
The Japanese ghosts featured in these movies are traditionally depicted based on local burial rituals. Japanese corpses were buried in white gowns, and women's hair, which was typically worn up during life, was worn loose for burial. Of course, Americans were first exposed to this kind of long-haired, white-clad ghost in the Ring, and have spent the subsequent 20 years saying 'This ghost rips off the Ring!' even if the movie they are talking about was produced in 1964.
OMG nineteenth century artists, think of something original!
If you want to make a horror movie and you can't think of a good plot, be sure to dip into the wellspring of rich, non-copyrighted culture that has formed around the Bible over the course of several thousand years. Never mind that you are taking the deeply-held beliefs of hundreds millions of people and using them in order to show people getting eviscerated or Paul Bettany firing two machine guns at the same time, or that your theological knowledge mainly comes from watching The Omen when you were fifteen. By associating yourself with the Bible, your movie will look much deeper than if you had just gone with the flying monsters you thought up yourself and named "Destructotrons."
Be sure that you pick the right types of biblical symbolism. Rods, green pastures and shepherds will probably not do. You should go instead plagues, demons and raining fire, in no particular context or order. If you are reading the Book of Revelation for demon ideas, and come across a verse about a woman in labor, throw that in there as well! It will all make sense somehow.
Admit it, this movie would be freakin' awesome.