Sometimes you need a title reveal to make the connection.
The trailer for Prometheus is made up of largely disconnected imagery, with a slow reveal of the title - in the same way Alien's title was revealed - over it. There are some great alien planet vistas and space shots and some looks at our heroes in space suits and firing guns and running around. There are some intriguing shots - someone getting a facehugger made entirely of goo, and a Space Jockey head on a medical table for an autopsy. Repeated viewings will surely pay off small details.
But it's at the end that we get thereal payoff - we see the Space Jockey's ship from Alien. We see it exploding - possibly a flashback? - and then standing on its side... before it falls over. So now we know we'll have the mystery of 'Why was that spaceship laying down' answered for us.
I like the trailer - it's way more of a teaser - but there is one thing I really, really don't like, and I hope it isn't nitpicking. As the ship is falling we have one of those shots of somebody running away from calamity. And it's the same one - actor looking right at and running towards the camera, the background filled with CG destruction. This is one of the lazier shots in modern filmmaking, I believe, and it's disheartening to see the trailer ending on it.
Otherwise, everything else looks great.