Conventions of teaser horror trailers:
Intertitles: Set up the premise of the film and provide explanation when necessary. They also enhance the audiences understanding of the plot quickly.
Editing: Mix between continuity and montage editing. Allows for plot to be developed quickly, and for the most exciting parts of the film to be shown, while still going into certain parts in detail.
Narration: Further establishes the story.
Sound: Non-diegetic sound is used a lot in horror movies, to create atmosphere, heighten tension and make climatic scenes more dramatic. Music can also indicate stress, panic, tension, signs of the plot unravelling etc often subconciously recognised by the audience.
Special effects: Effects such as altering the colour of clips can change tone and create certains atmospheres. For example, in the film Paranormal Activity the hues are mostly blue - this gives a cold, eerie appearance and also replicates footage of a surveilance camera. Other popular hues are green and grey, as seen in Saw and Silent Hill.
Another effect that creates a handheld camera/supernatural feel is use of artifical 'static interferance' featured below (shot from Paranormal Activity 2). Often used to reinforce (or give the illusion that) the action was filmed for real, making it scarier for the audience as there is an element of realism added.
