I'd like to put in a request to
a) not give the ending away in the trailer. Even if we don't "know" it's the ending.. we'll be waiting for a scene that looks like that and if it's not in the first hour - we know what's coming next
b) While it's important to show how funny a movie is - using ALL the best lines (if there are only 3 or 4) is a mistake.
c) previews without any dialogue, any narration, that play like a video game commerical do nothing to sell your movie - even if it's just an action flick.
"A little nonsense now and then is relished by the wisest men" - Willy Wonka