The person you flee to for help is either the killer or in league with the killer. If it’s a supernatural menace, the professor/ museum curator you’ve been going to for information is the leader of a cult that worships it. If it’s a psycho serial killer, the sheriff is the killer’s brother or childhood friend who’s protecting him.
Except for the heroine who will obviously live through it, females are incapable of responding to a threat in any way but hysterical panic.
The nerdy guy, like you see all over this board, who knows exactly how to defeat the monster, is the first one eliminated.
Variation on the theme: He’s eliminated halfway through the movie, because his plan to defeat the monster requires the cooperation of the other heroes, who wouldn’t help the nerd if their lives depended on it (even though they do!).
I think a rare variation on the theme (and possibly a good variation) is when the nerd fakes his own horrible demise, because HE’S THE KILLER! Does anybody know of any movies where this happens?
Another cliche: The more ditzy the blonde (male or female), the sooner they’re eliminated. If the ditzes are having sex, they’re killed together. (Or one of them is the killer!)
The inbred serial-killer cannibals are alway rednecks – never preppies!
The killer in the movie that the Hero(ine) just killed is NOT REALLY DEAD, not even if the hero emptied an entire clip of ammo into the killer, set the killer on fire, and ran them through with a knife/sword/machete/the killer’s own weapon, they are simply waiting for the Hero to turn their back to them and/or look away, so they can kill the hero or escape and set up the plotline for sequels… the only way to truly kill the killer is to nuke 'em from orbit, only way to be sure
when the group of protagonists are arming to protect themselves from/attempt to kill the killer, at least one of the protagonists will forego a more superior weapon, and instead choose a flashlight…
“Hmm, lets see, i can choose a baseball bat, a katana (or other martial arts weapon), a handgun, a sawed off shotgun, a machete…naaah, i’ll just take the flashlight”
Right above her elbow, a woman has a NO O/D button. She’ll burn more gas, and it’s rough on her tranny, but sometimes you need that extra torque.
Uh, huh. That is just what I would EXPECT you to say.
Folks, they’ve already taken over pinkfreud! Do not listen to her. Do not believe her!
I’m reporting this post at once. Maybe it’s not too late for the rest of us here…
There is always a creepy old man/townsperson that warns of dagers “in them thar woods” or island or campground or…
I ment “Dangers” in “them thar” etc…
The authorities will always vastly underestimate the severity of a threat and will react to it in a manner guaranteed to fail.
Or: any person sitting in a vehicle will turn out to have been killed and will slump forward as the potential victim taps on the glass asking for help.
Why they don’t just dump the body & see if the car will start I’ll never know - oh right, horror film logic 
Or wearing footwear with heels long and sharp enough to act as crucifixion nails, yet attempting to run.
For some reason they never use the freaking heels to nail the vampire.
Serial killers are either urbane geniuses with extremely well developed communication skills, or reclusive pschobillies who can barely stammer out a word.
If you manage to escape the psycho killer and reach the cops (or other authority figure). It won’t do you any good. Either they won’t believe you, or they’re into the whole psycho killer thing themselves.
The scene where our hero is in the bathroom in front of the sink looking in the mirror on the medicine cabinet. They open the medicine cabinet to get something.
Then when they close it they see REFLECTION OF BAD GUY/GHOST standing right behind them!!
The psycho killer chasing the blonde bimbette through the woods, all the time yelling at her, “Come back here. I won’t hurt you, bitch!”
If someone mentioned this already, I’m sorry. Here are two that always bug me:
1: The cell phone that suddenly won’t get a signal when the monster/killer/alien is after you. Variation is the one that does get a weak signal just so the caller can go “Hello? Police? The monster is here! he’s chasing me by old McDonald’s farm! Help”. Followed by the police dispatcher saying “Repeat that? where are you?” and then the signal cuts out.
2: The car that won’t start FOR NO reason! Everyone has seen this. Even if its a freakin’ NEW car and the characters have been riding in it prior to meeting the monster/killer/alien with no problems, it won’t start when they need to get away. Variation of this is they fumble with the keys for ten minutes but can’t get them in the ignition and the monster shows up and kills them or at the very least trashes the car.
1.) If you manage to get the gun/weapon away from the bad guy
a.) Use it on him with utmost urgency, dismemberment is always best.
b.) DO NOT LEAVE IT ON THE GROUND NEXT TO HIM/HER/IT.
2.) Might as well not run, as the baddie will only walk and still end up in front of you at the next tree/corner…
What’s really ridiculous is, this cliche persists in this age of electronic fuel injection and computer-controlled ignition.
This is more of a Stephen King cliche than a horror movie cliche per se, but you see it elsewhere as well. For purposes of brevity, let’s call it the “psychic retard”. That is, there’s some mentally disabled person who knows all, or is the key to solving the whole situation, or is just plain powerful in some magical or semi-magical way.
When being pursued by a serial killer, the woman will, sooner or later, trap herself by running upstairs.