Book trailers have only come along in the past decade. But they are rapidly becoming a staple of press kits and grass roots promotion. A well-done book trailer can help sell you as a talk show guest or news interviewee. Some TV stations may even use your video as b-roll during your interview.
You can post your book trailer to your blog, Facebook page and website. You can send it with your press releases. You can put a link in your Tweets and other social media. You can add the link to your email signature.
Please get professional help in shooting and editing your book trailer. I may be biased, but my husband's new trailer is a good example. He is an Emmy-award winning producer, so he has an advantage, but he's not used to being in front of the camera. Take a look and see what you think he does right.