Book trailers range from a video of the author reading a passage from the book to (loud) techno rock and a short slide show consisting of the book cover, a promotional paragraph and a photo of the author.
I did some searching on Google. Here are some book trailers I like.
This one is Harry Potteresque:
Another impressive one:
Now for non-YA book trailers:
A very dramatic one:
And one non-fiction trailer:
Warning: this one is loud, but diabetics will love it:
How much do they cost?
For all you do-it-yourselfers:
If you want a workshop: http://booktrailersforall.com/professional development.htm
Once your book trailer is complete, besides You Tube, you can post it here:
Or here: http://booktrailersforall.com/
If you have a book trailer you're proud of, don't be shy; post a comment with a link to it.