Own trailer review 1: Grave Encounters (2011)

What happened in the trailer? 
In the trailer, a team of 'paranormal investigators' lock themselves into an old mental asylum for a tv show pilot episode. Supernatural stories are told by various members of the public, and there is also some video evidence shown. Whilst the crew are in the building, supernatural occurences happen, ranging from carvings on chests to lights getting blown out.
Which positive, clever or interesting aspects do you think you could include in your own trailer? What generic features are fulfilled well?
The trailer creates suspense and horror, especially at the part when the window opens mysteriously. the trailer shows a lot of action and screaming and not a lot of the film, so it makes the film worth watching because you haven't already been told everything that happens (and in sequence)
Which aspects of the trailer did you think were unsuccessful? And what would put off it's target audience?
I thought that the trailer shows too many scary parts of the film, and it seems to spoil what I think would be the best scares.