A trailer and a film are two different animals... I've always thought there was value in bringing in a new editor, with fresh eyes for a trailer edit.
If I'm doing it myself, I try to forget the story of the movie... go back to my logline, the idea that sold me on this particular movie... and then try to turn that logline into a 30/60/90 second film.
The worst mistake I've ever seen a producer make on a trailer, was to leave out the chase footage from the last act, because he didn't want to give the ending away.
Only other piece of advice I'd give is cut a trailer... put it aside for a week, then go back and cut a completely different one... then put both of them in front of people you trust and ask them which they preferred... and ask them what they thought the film was about? And which one had they think had the largest budget... trust me, a good trailer edit can put $40,000 on your perceived budget.