Book Trailers

I absolutely love watching movie trailers. Even if I've already seen the movie, I'll watch its trailer just for fun.
With the relatively new trend of book trailers getting underway, though, trailers may have moved up a notch or two on the significance scale for writers.
I'm not saying you should be pouring time and effort and finances into producing a trailer for your book at this moment. Several publishing houses have started adding professionally-produced trailers into their marketing strategies, and I know of at least a couple of organizations that specialize in producing book trailers for writers. Until the publishing process is solidly underway for you (as in, the papers are signed and it's time for some serious and specific marketing), focus on the writing itself, building your platform, and establishing a fan base, not on making a trailer. When it is time to think about a trailer, your editor, publisher, or agent can help and advise you.

All that being said, in the meantime it sure is fun to think about those fabulous 'trailer moments' in your writing, isn't it? And there's a lot to be learned about what makes a good trailer just by watching big-budget movie trailers.
My all-time favorite movie trailer has got to be the one for The Hunt for Red October. Even though I've seen the movie itself multiple times, watching the trailer still makes me think "Oh wow, I have got to watch that movie!" Two of the best 'trailer moments' ever (in my humble opinion): the shot of the submarine rocketing out of the water, and the close-up of Captain Mancuso saying "I'm gonna blow him right to Mars."
The trailer as a whole could be a textbook on how to make a good trailer. It has a good balance of dialogue shots (giving the viewer some idea of what the story is about and who the main characters will be), voice-over (adding intrigue and filling in any problematic gaps in the viewer's understanding of the story's setup), action shots (for excitement and drama), and a few choice scenes and snippets to raise questions, confuse the viewers, and make them want answers (i.e. see the movie).
Those are the same qualifications a good book trailer should meet too. I've seen book trailers that explain the book's basic premise, but don't give any idea of who the main characters will be or of what the specific plot will be about. I've seen book trailers that explain who the characters will be and what the storyline is about, but don't intrigue me, leave me with questions, or make me want more. I've seen book trailers that show lots of cool action shots, but don't give me any idea of what the plot is about. I don't think I have to explain why all of these are problems.
Remember, the whole point of a book trailer is to make the viewer want to read your book. Therefore, it should provide them with the information they need to decide whether your book is for them or not (Is this an action/adventure story or a calm, quiet love story? Is the main character's biggest struggle with a moral decision or a world-altering war? Is there a definite Christian theme here or not?). At the same time, it shouldn't give them so much information that they know what's going to happen and give them no reason to bother reading the book.
Finally, it should be exciting! Every good story has its 'trailer moments'. You know what I'm talking about--that scene or shot or moment in your story that just makes you break out in goose bumps and want to do a happy dance just because you're the one who wrote it.
In my current WiP, my favorite trailer moment is the moment when one of my characters (who has just escaped from the enemy and is running for his life) picks up a handful of sand and throws it back towards the enemy camp. As the grains of sand leave his hand, each one becomes a spark. The sparks flare into a firewall and cut off his pursuers, leaving him free to make his escape. Does that moment tell a reader or viewer anything essential about the nature of the story? Probably not. But it's a dramatic action shot that will build excitement and get a reader or viewer 'wound up' about the book. (And yes, when the time comes to start seriously thinking about making a trailer, I plan on making sure that shot goes in it.)

What are your thoughts on the book trailer trend? Do you have a favorite movie or book trailer?
Writers, what's the best 'trailer moment' you've ever written?