What makes a good film trailer

In a typical film trailer there are usually scenes from the film. They are mostly the best bits of the film to make people want to see it. There is also background music. This is something that indicates the genre of the film the trailer is about. For example in the Avengers trailer there is dramatic music in the background when there is fighting scenes. There is sometimes also a voice-over man that speaks over the trailer. They are usually used for action and thriller films because they have the most dramatic scenes. At the start of a trailer there is usually a production company logo.