Ok, so the trailer isn’t actually revealed, but there is a descrption of it making the rounds on the internet.
According to ComicBookMovie.com, an uncredited source describes the teaser trailer for Green Lantern that will be shown before Harry Potter and the Deathly Hallows Part 1. Now, since this is an uncredited source, it does not exactly give it much weight. That’s not to say that it doesn’t sound plausible, but without a reputable source (or even the actual trailer), I’m going to take this with a grain of salt.
That said, this could be a description of the actual trailer. So spoiler alert!
They show Abin Sur [a Green Lantern] crashing, then you see Hal Jordan standing over Abin, they made him look a little different than what we’ve seen in the comics and movies, instead of a mostly human shaped face, he seems to have these (for lack of a better description) what looks like curved horns pointing down from his jaw line. They’re not horns but the best way I can describe it (MrDCU: What he is referring to is the almost elastic looking way Abin’s Skin is if you have seen the ComicCon pictures you know what I mean). Then they show him with the ring. There’s a scene with Hal and Carol in the locker room going back and forth a bit, Hal makes a comment about her helping him with his pants. There’s a scene with him talking to Tom about him not having fear and his friend gives him a look and he goes “yeah I know”. Another scene where Tom’s sitting on a couch and Hal goes “Check this out” and he instantly changes into his costume. Tom goes “That’s cool” Hal: “I know” Tom: ”What do we do now?” Hal shrugging: “Go fight some bad guys”. A scene where Hal makes a huge fist construct to right hook a bunch of bad guys. The construct looks solid with what seems like mist coming off of it, don’t know if they’re trying for an excess energy look…, There’s also a scene where he’s taken up to what looks like a ring in space that shoots him into hyperspace to Oa [The Green Lantern home planet]. It was a quick long shot of it, but that may be the way they are explaning what Abin Sur crashed in. They show Oa briefly. There’s a shot of Hector [Hector Hammond is the bad guy who has a giant head and telekinetic and telepathic powers] looking normal, then there’s also a quick shot of Hector with a bigger head.