I did a little unit with my video class on editing movie trailers. We looked at about 20 old horror film trailers, then some trailer mashups -- for example, one that makes "The Shining" look like a Romantic Comedy and one that makes "West Side Story" look like a zombie movie -- and finally a few contemporary trailers.
One of the big points: the old techniques of Persuasion still apply, not any that different from how Aristotle thought of them.
You appeal to the emotions, trying your best to show a viewer that they can identify with the characters in the film and that it will make them feel a certain way. You appeal to the viewer also based on the reputation of the filmmakers and the actors in the film and the reviews the film has received. And you make a case that the film is about something the viewer should care about and want to see.
Beyond this: the marketing folks insist: there must be five "movie moments" -- five images one would want to see, selling the experience of seeing the film.