Trailer Help

There's no doubt that making a trailer is a hard thing to do, especially when you don't have an actual film to work from.  So the best thing you can do is keep looking at real trailers to inspire you and help you structure the thing.  Just had a look at this trailer for a new British drama and think it contains lots of useful reminders of what you should be trying to achieve.  Pay close attention to the structural devices - the dialogue as voiceover, the slates etc.  Most importantly look at how few sequences there are and how, where present, they're no more than three or four shots.  The script really does the job.  Dialogue is minimal, one line here and there that sums up the narrative thrust, e.g "we're not kids any more" telling the audience about genre and narrative. 
What this tells us is that you need to aim to 'strike and run' with your shots.  They should grab the audience and then you move on to the next one that grabs them and so on.