The Language of Cinema Cliche: This is how you know that ...

When a notably pretty but bookish girl puts on too much make up, the other characters will realize that she - gasp - beautiful.

When a coach gives an inspiring speech, a hapless ragtag bunch of misfits will surge to a championship.

And of course, “roughly age-appropriate” usually means 10-25 years younger than the male lead.

This also works for disaster movies.

Cops who are about to retire will die, usually one to three days before their retirement party. [Chief Wiggum] We call it retirony[/Wiggum]

Those who are dying will always have enough time left for a last speech no matter how horrific the wound.

Rolling out from underneath someting instantly identifies a character as a mechanic (Joss Whedon makes fun of his own use of this cliche in the Firefly commentary). Likewise, any character in coveralls and cleaning his hands with a rag is instantly recognized as a mechanic.

Pizza boxes identify an apartment as crappy no matter how much space or how little grime there actually is.

Sunglasses represent the person. It used to be that aviator-style sunglasses were associated with tough guys, but now they let you know that the character is a jerk, especially if they’re tinted brown. Cat’s eye sunglasses mean the character is full of ginger. Round or oval sunglasses, especially if they are tinted in red or green, mean the character is hip.

Characters seen chewing are recognizable as assholes, whether it’s the gum of an obstructive secretary, or the tobacco of an aggressive redneck lummox.

A tie with a short-sleeved shirt means the guy is a regular working stiff. A tie with a long-sleeved shirt is more likely to be worn by a shitbag.

Potential love interests in a mixed-race cast can be predicted by matching skin tones.

A car shown moving through a haze of heat brings trouble.

In horror movies, any girl that removes her shirt is doomed to a grisly death.

Also, she will give birth at the most inopportune time possible.

A character pointing a gun at another character implies “I will shoot you.” When he cocks the gun, it implies “And I mean it.”

SCUBA masks are decorative only. It’s perfectly possible to see underwater without one.

Villains hate to see themselves on the TV news, yet they are unable to turn the set off themselves. They must always get a henchman to do it for them.

A major actor in a minor role is the murderer. :smiley:

Bartenders also carry rags, but they are always polishing pint glasses with them.

If the good guy is evenly matched WRT having a gun, or has one and the bad guy doesn’t, he’ll lose it. You must then see the gun fall to its doom in an irretrievable fashion, just to hammer the point home. (Down the side of a cliff, into a dark chasm, clanging echos all the way down, off a speeding train, etc)
The less the filmakers know about computers, the more noise they will make while characters use them. (Ex: every keystroke beeps, “password denied” screen flashes and makes “wrong guess” noises)
Movie computer hackers are the fastest typists in the world, and rarely use the mouse or any sort of UI whatsoever. Sometimes they only need to use one hand. (Goldeneye, Swordfish)
Two characters struggling for a gun that goes off have to both behave as though they’ve been the one shot - freeze, eyes wide, slowly let the other one sink to the floor. Rather than what would probably really happen - the unshot one easily taking the gun away from the real wounded one, shoving him off of him, and shooting him a few more times.
In older movies, characters that are secretly stabbed in the back simply stop talking and look astonished, rather than say “AAAAAAUUUGHHHH!!! OH MY FUCKING GOD I’VE BEEN STABBED!!!”

Anyone on the good side that is shot or stabbed or otherwise undergoes severe trauma will live just long enough to have a short, parting conversation with the hero. This is true especially if it occurs after the opening act. If the character is borderline or somewhat bad then they will have an epiphany and do something to help the good guy just before expiring gently.

Here are some of my random movie-convention observances:

No matter the current prevalence of plastic grocery bags, a character is known to have been grocery shopping by the presence of brown paper bags with a loaf of French bread protruding from the top of one.

When the camera is focused on someone wielding a gun from the front, you know that the next shot will be deadly-accurate if a short depth of field is used, and the focus shifts from the wielder’s eye to the tip of the barrel.

A view through binoculars is always indicated by masking off everything but two overlapping circles. Likewise, telescope/sniper rifle use is indicated by masking off everything but a circle, with the difference between the two indicated by the presence (or lack of) cross hairs.

If someone is leaping across a gap (as in a rooftop chase scene), a camera shot from directly above or below the jumper always precedes a successful jump. However, a camera shot from behind the jumper usually means that they’ll barely make it, a probably have to pull themself up the other side.

In kung-fu movies, the Westerner who fights with mostly kicks is a bad guy.

In Sci-Fi movies, any sort of green glow associated with a newly-encountered alien species, be it from their highly-advanced energy source, the beams from their weapons, or their eyes, means that they will somehow be a threat to human existence (or at least the existence of our heroes).

The bad guy’s sidekick is usually a bumbling idiot. If there are several bad guys, at least one of them will be done away with by the leader for screwing up. The leader of the bad guys is always the last to be eliminated as all his henchmen get picked off before him.

Who often gets pissed off at being called a bumbling idiot and turns on the bad guy. Or does it because he’s not really a bad person and has an attack of conscience all of a sudden.

An old man who is suddenly killed with the main good guy character as the witness to the death will have something very important to tell him/her and the old man will say it in a very clear and coherent voice.

Especially if guesting on any Law & Order show.

Or a brilliant manipulator who is planning on offing his boss after the most risky phase of the plan is complete.

The sniveling double-crosser who sold out the hero will always be the last one by the hero’s side in the big fight.

The grouchy malcontent who didn’t want to go on the mission will die heroically saving the rest of the team.

A sweet, naive, pretty young woman always has a wise-cracking, knowing best friend.

The last second before the ambush lasts three and half minutes.

The more beautiful the villain’s girlfriend, the more likely it is she will fall for the hero.

An unattractive teenager is a dangerous misfit. An attractive teenager is a valuable sidekick.

All 11 year olds are either smart-ass distractions or brilliant computer geniuses.

A couple of weeks ago, I rented an Australian movie called Russian Doll.

The oddest thing about the movie to me was that most of the major characters smoked, and there was nothing symbolic about it. Smoking didn’t indicate the villain; there were no seductive smoking-related interactions; smoking was not a sign of moral weakness or gullibility… it was just an unimportant but frequent part of their lives, like walking along the street.

If a character gets into a car and we cut to an extreme wide shot, the car is about to blow up.