Government - a surprising number of feudal-style empires exist in the future, probably because teenage boys think titles (like Duke Leto) are cool, and want to envision themselves part of the privileged class.
Either that or a repressive, Big-Brother-like police state that somehow can easily be defeated by a handful of rebels, usually connected with blowing up the enemy HQ or doing away with the Head Bad Guy.
Clothing tidbits: Big swoopy standup collars, often attached to the abovementioned capes. And little puffy crescent-shaped ridges running fore-and-aft at the outside edge of the shoulders. Early 50s space crews also wore a lot of baseball caps.
Radio or two-way video communications often exceed the speed of light, allowing protagonists to taunt one another planet-to-planet in real time.
The rule of three, as a comedian once said. In any list of famous people recited by people in the future, two will be from our own past and the third will be from our “future” as in “Yes, he’s worse than any of the conquerers of the past: Alexander the Great, Ghengis Khan, or Krylol of Rigel 4.”
There don’t seem to be any farms in the future - only vats of sludge, hydroponic tanks or (gack!) Soylent Green.
Nobody mows the lawn, tinkers with their personal vehicle or paints the house. Robots clean everything, and kitchen implements prepare food themselves.
Many household robots have semifake English accents.
The couple who make it safely away from the repressive society/exploding spaceship, etc and land their barely operable lifeboat on a fresh green virgin world will turn out to have names that are some recognizable variant of Adam and Eve.
And so on.