All spacecraft–including starships which are supposedly capable of traveling many times faster than light–are maneuvered by having some guy haul on a joystick while he peers out the window (or occasionally at a “viewscreen”, which shows exactly what he’d see if he looked out a window). Weapons are targeted and fired pretty much the same way, with someone manually lining them up on the target and then pushing a big red button. These weapons have a range such that in order to engage in combat, spaceships have to get close enough to each other that the crews could just as well throw rocks.
No great literature or cinema is ever produced after the late 20th Century. Ten thousand years from now, people are still watching Humphrey Bogart movies and quoting Shakespeare.
Animals are rare in the future. Not many pets, dogs, cats, fish, zoos, anything. Not many household plants either.
Nobody dresses real casual–blue jeans, tennis shoes, etc. Not much formal dress either (suits and ties, or women’s dresses), except for formal military uniforms.
Humor and laughter are rare in the future. Maybe because almost every day is a work day. Not many weekends or holidays.
I think Futurama may be the best sci-fi show that doesn’t fall into these stereotypes. People live on Earth, have regular jobs and lives, are not constantly fighting aliens. So far, that show is perhaps the most reasonable prediction of what the future will be like.
There is no idiom in alien languages, forcing aliens to resort to English whenever they wish to make a point, even when they’re talking amongst themselves. “We have already discussed this. What is it the Earthers say? Don’t beat a dead horse!”
Aliens are always incredible imitative of human culture (this started LONG before the Star Trek episode “A Piec of the Action”) but humans are NEVER imitative of alien culture. We don’t convert to alien religions, either (I’m talking about bad movie, TV, and comic SF, so don’t give me any lip about “Stranger in a Strange and”).
Off-line data storage is on crystals/chips/whatever that are often inconveniently small and have no provisions whatsoever for external labeling.
I’m not really bothered by the lack of toilets in the future, since non-SF tends to have a lack of toilets as well. Let’s face it, movies about people sitting on the potty just aren’t that dramatic.
Also, all computer systems in the future will be compatible, no matter how disparate their origins.
And all spacefaring races will agree on a universal “up” and “down” and align their ships accordingly.
No one ever destroys an enemy starship simply by exploding a big nuke near it (exception: Babylon 5)
Parasites that evolved in a totally alien ecosystem find humans just right for their needs.
A damaged spacecraft will always “crash land” on a planet that just happens to be nearby.
99% of all evil aliens can disguise themselves as humans.
The artificial gravity never fails. (exception: Star Trek VI)
A spaceship can be reduced to a battered hulk filled with wreckage, yet still retain pressurized compartments.
In a brightly lit room, you can see stars out the window. (try this at home one night).
The human race never gets it’s butt kicked by superior aliens (exceptions: Babylon 5, Futurama)
Well, Ben Sisko not only converted to, he became the Messiah of and later a god in the Bajoran religion…
(The 2 sides of the Bajoran religion - Worship of the Prophets and of Pagh Wraiths seem fairly compelling…the latter managed to get Gul Dukat to convert as a very devout - actually, zealous - member - in fact, he became the Anti-Christ to Sisko’s Christ. Not to mention Rom’s apparently converting for Lyta’s benifit. Of course Dukat and Rom are aliens, not humans so they don’t really count…)
There aren’t any billboards or bumper stickers.
People don’t call each other “snookums.”
Most of the smart, developed alien races are bipeds.
Nobody wears t-shirts that say “Kiss me, I’m Romulan.”
Nobody has real metal keys – only keycards.
“2001: A Space Odyssey” did a humorous turn on this. Not only did the Earth-orbit-to-Luna shuttle have a toilet, the toilet came with a wall-sized panel of instructions–in small print. By the time one gets through the instructions, one no longer needs the toilet.
Gotta love the Fifties…
Ships have cooks on their crews, and the cooks speak with Brooklynese accents, wear Gilligan caps and wear white cloth aprons even when they’re not working. They’re always in search of “hootch… oh, but only for cooking.”
Any Spider monkey brought along with the expedition is always is the first to discover that the new planet has a breathable atmosphere.
Talking robots are plentiful but stationary computers are massive. And robots talk but stationary computers can’t.
Space expeditions bring .38 longnose revolvers. They sure come in handy when the expedition goes into the cave and gets pounced on by the big-ass spider.
The women on Venus are always desperately in need of men, haven’t had any men around since God-knows-how-long, yet there seem to be plenty of Venusian women. They’re all Caucasian and show no signs of lesbian tendencies.
-Every future weapon is a laser… bullets no longer exist.
-Deflector shields always form a massive sphere/ellipsoid around the ship it’s protecting, making a bigger target and an apparently inefficient system (they’re protecting a volume twice as big as the ship!).
-No porn (unfortunately).
-Children are always prodigies. And they often grow at an accelerated rate, too.
-The necessity to aim a hand-held weapon has disappeared, so much so that weaponry no longer has any aiming apparatus (and it’s shaped like a TV remote control, too).
-Plastic is stronger than metal. At least when body-armor is concerned.
-The Evil Emperor’s personal guards are always armed with spears/axes.
-You can always sneak into someone’s secret base through the air ducts.
Wondrous tours of alien cities are mentioned in the Captain’s log, but never seen. Aliens (on Star Trek, anyway) never have brand names for their food products. I recall an episode in which a little alien boy (I knew he was an alien because he had a piece of latex glued between his eyes, and a small artistic tattoo just below his left ear thus making him totally non-human) was once advised to go buy himself a “confection bar.”
1954 DeSotos have bubble domes thus making them the car of the distant (THE YEAR 1988!) future.
Brylcreem has made a comeback.
If the film was made in Europe in 1966, the future is very mod, pop-arty with lots of white walls with random black dots and designs.
3-D Comic Books in the dentist’s office.
A tendency to, without much context, mention the ancient days of 19?? (coincidentally, just about the year the movie was released).
World government–The President of Earth (“Madam President”).
Until the 80s and 90s, with notable exceptions, there seemed to be very little ethnic diversity in the future. Everybody was as white as Roger Whitaker.
Time-traveling heroes humourously attempt/misunderstand slang.
Speaking of which, slang is taboo in the future, or else it’s along the lines of “As they used to say in the 20th century, ‘Right on, man.’”
This one annoys me to no extent. Star Trek, again. A hundred years from now, people jam on Steppenwolf, etc. Yeah, I so dig the pop hits of 1878, doncha know.
Sir
Spaceships are aerodynamically designed, and manouvure through space as though the were banking in an atmosphere.
When travelling out of the solar system in a straight line you will pass by every single planet.
Everyone travelling back from the future is coming from 1999, 2000 or 2001
In the year 2000 we posess interstellar flight, but communication devices identical in size, shape and operation to old style walkie talkies.
Cars can fly.
Heavy makeup on a man is a sure sign that he’s an alien.
All planets have a breathable aptmosphere and have recognisable plant life, although it might be painted purple.
Aliens deferentiate towards the obvious intellectual cultural and social superiority of humanity.
Humans can interbreed with creatures who evolved on an entirely different star system and have a completely different style of reproduction, yet experiments conducted by lonely farm boys on local sheep from the same evolutionary cradle have produced nil results.
Hey, this is really fun!
This is something we should definitely strive towards ensuring never happens. Let me be the first volunteer to begin colonization on Venus, please! 
goboy, I almost fell off my seat laughing.
In the future, It seems there is either still an earth with the same pollution/population problems, even if it’s five thousand years from now, and yet, we still get along fine, or earth has been destroyed by some menacing alien force without any warning (or perhaps a small warning left in the filing cabinet of some basement on some distant planet by the vorgons…) and yet Humans still manage to survive…
-Door knobs. They won’t exist. All doors slide open and closed from the side.
-People don’t seem to bath or shower much in the future, but they look clean and nobody complains about body odor.
-The paperless office arrives in the future. People hardly ever use paper, pen or pencils. Not many printers, copiers, or faxes.
-There aren’t really any offices either. Everybody sits in a big open area at their “station”.
-Nobody smokes or chews gums.
-Telephones and phone numbers don’t exist. Everybody uses walkie/talkie communicators. How are these communicators able to reach whoever you need to at
the time without using a phone number to reach them? You just turn it on, say your names, ie “Kirk to McCoy”, and the other person is there. What if there are
several McCoys, or the person you need to reach is named Smith?
-Hull breaches can be fixed. Just seal off the sector and fix them.
-A lot of planets have oxygen and air pressure similar to Earths.
If hardcopies exist, they are in the form of plastic transparencies. 'Cause those are so easy to read.
There is always a tribal elder who remembers the last 6,000 years (pardon me, cycles) of history that somehow didn’t get recorded, but dies just before he can reveal what the members of the civilization did the last time they were threatened like this.
The civilization’s queen is the most beautiful and usually the most intelligent member of the community, but inevitably falls for the earth commander five minutes after they meet.
All physicians have come to accept the healing powers of a good stiff drink.
All planets with breathable atmospheres are either lush jungles or deserts. No other planet seems to have a prairie.
Despite the rigorous screening procedures and training that astronauts undergo, every crew contains either a hothead, a coward or a traitor.
Ship’s weapons are never effective, but something quickly jury-rigged will always have devastating destructive power.
Patrolling guards will lose all peripheral vision.
Evil guards’ body armor will be entirely useless, especially against small furry Ewoks throwing rocks.
I dunno about this one. Quite a lot of your lower-budget planets bear a truly amazing resemblance to random places in Southern California. Of course, it’s true that your higher-budget worlds all have ecologically-unlikely single-biome planetary ecologies (“the jungle planet”…“the desert planet”…and also “the swamp planet” and “the ice planet”). It’s especially interesting that the “desert planet” and the “ice planet” still have perfectly breathable atmospheres, given their pronounced paucity of oxygen-producing vegetation.