Conventions Of Film Trailers

Generally film trailers consist of four elements.

Plot summery: Establishing the scene, Introducing the characters and show the problem they will face (However it is a trailer therefor they cant tell you the outcome)

Voice-over: Tends to be a strong and powerful voice to attract attention. Gives a brief explanation as to what the film is about.

Music: Helps to set the tone and mood of the movie. The music which is on the trailer isn't necessarily from the film itself as the score or soundtrack may not have been developed yet.

Cast, crew and studio information: The cast, producer and director of the movie is revealed by showing their names usually in text format. Studio production logos (producing company and the distributor) are also shown, they originally featured near the beginning of a trailer however since the late 1970's they were shown at the end.

Mise-en-scene
Sound
Lighting
Language
Editing
Cinematography

Is used throughout to create the atmosphere of a particular genre.