This could either be:
Freeze Frame
Slow Motion
Fades
Wipes
Fast Pans
CGI
Captions
Director
Producer
Actor
Release Date
Sound Track
In a trailer you are unlikely to see a long shot and instead you would see fast cuts from one scene to another as they don't want to let a lot of scenes out.
To emphasis the trailer they insert close ups which could either be someone holding a weapon or the back of someones head. This is used as in teaser trailers you are not given a lot of information so the close ups is to show the main shots to make the audience think about whats going to happen.
IF the film is Paranormal Activities then the visual style would be hand held documentary realism where you would have the characters holding the camera instead of a camera man.
All characters in a teaser trailers are all important as they could be either the hero, villain or a suspect. The trailer wants to introduce us to a character like Liam Neeson's character in A Walk Among The Tombstones as he tells us about himself.
Is used in mostly action shots and suspense moment.
For example in the Expendables trailer you have a lot of action scenes which only stay for a few sceonds and moves straight away to the next one.
Every shot should be there for a reason in teaser trailers they want you to be aware of who's character is like and what happens.