Copy+Paste from Mad Max (desert setting, everybody wearing bondage gear, tricked out cars).
Incompetent military and soldiers with aim as good as a stormtrooper's aim, oh and they're all just heartless, evil monsters that act as cannon fodder for the protagonists
Nobody bothers trying to rebuild society, they just like living squalor or getting anally buttfucked by highwaymen.
Weapons and armor pieces made from salvaged road signs and car parts (I kinda like that though).
If it's a movie or video game, either bleach the colors out completely or saturate them. The lighting is either blindingly bright or way too dark. Bonus if you apply an ugly color filter to the game on top of all of this.
Some crazy cult that worships whatever caused the apocalypse
Nobody knows anything about guns, if this is a YA story, then make it very clear that you not only know absolutely anything about how they work, but also be able to somehow shoehorn your "guns bad" political views into your story.
To add on the last statement, stories about how all electronic items stopped working, yet somehow guns also magically all stopped working despite being 100% mechanical.
The start of the apocalypse is either: nuclear war, dwindling resources, global warming, zombies, god or satan deciding to destroy humanity, or an epidemic that somehow magically killed 90-99% of the population.
And said cannibalism not resulting in Creutzfeldt–Jakob disease or other related variants of kuru.
Another stupid cliche: All good people immediately abandon religion completely. Anyone who professes a faith (almost invariably Southern Baptist, but can be any religion and denomination) is either a mindless cultist or an evil monster who is just waiting for an opportunity to rape the female lead. This, despite the historical reality that people will tend to rediscover religion in hard times, if only because it gives us comfort and courage, and only tending to abandon it en masse during good times.
A scientist has the cure, but nobody except the hero believes in her because sexism or something. She also is super-hot. Bonus points if she also does martial arts better than the men.
The black guy dies first, too.
Oh my god, all of this right here. Also big bonus is when the females die, their deaths are almost always off screen or extremely merciful for the setting (getting shot in the head, poisoned, falling from a great height, etc).
Plus you also basically summed up most apocalyptic YA stories in a nutshell.