Haunted houses are never locked. Murders will always be accompanied by sinister music. Rich people are unhappy. When someone is dead or dying, there will be a trickle of blood from the corner of their mouth. Christmas Eve and Halloween night last for three of four days.
Midnight happens more than once in a monster movie.
To kill a vampire, you must set out 5 minutes before sunset. Nobody ever realizes until the end of a monster movie, that everyone that went into tht dark cellar never came out. The group always splits up to look for the alien. Movies based on true stories are always made up. Computers never crash.