1. Someone fighting for his/her life will look elegant even if s/he is temporarily being beaten. In reality, life-or-death fighting is ugly.
2. The hero hardly ever reacts honestly in a dangerous situation. It's usually only the poor extra character (slightly villainous, or the comic relief) who finds his bladder control going when suddenly finding himself in danger. The sole exception I can think of is in the Australian film "
The Interview" (with Hugo Weaving).
3. Death scenes usually give the dying character a chance to say something cheesy or moving before departing this mortal coil.
4. Liars hardly ever succeed in carrying off their lies. As a rule, they're found out in films.
5. When the hero pretends to be intimidated by the villain in order to buy time or inch himself closer to a weapon, the villain will almost certainly be fooled by it.
6. Houses and flats are impossibly neat. No one seems to have to dust or wash or clean anything - except dishes, of course, because such GOOD heart-to-hearts can be had over the dishes.
7. If you're a main character in a crime series, at least one (and almost certainly more) crime will be shown to be "this time, it's personal".
8. Employers don't dismiss rude employees who shout at them. Instead, they just shout back, threaten them with dismissal and do a lot of tight-lipped eye contact.
9. There's always "a" bar... or pub... where the main characters go.
10. Characters wear clothing they could actually not ever afford with the jobs they supposedly do.