Public relations is difficult to understand. It can't be bought, it can't be controlled, and it is never guaranteed, but there's simply no better way to gain credibility and momentum for your book.
First and foremost, you must understand that PR is not the same as advertising. Advertising is paid publicity. Therefore, you are guaranteed space in a publication simply because you paid a fee. PR, on the other hand, is unpaid publicity. You can't be sure that you'll receive coverage in a given publication just because you've contacted them. But, if your book is featured, it's more trustworthy because a third party (the journalist or editor at a publication) felt that you were a worthwhile story. Thus, PR can yield higher rewards than advertising when it comes to credibility.
A press release is the most important tool in public relations. It is written like a news story, but is meant as a suggestion to the journalist. You or your publicist will draft your press release and send it to media outlets. From there, editors and journalists will decide if they'd like to use you and your book as a story. If they do, they'll usually contact you for an interview. Press releases are rarely run word for word.
It's a good idea to put the most newsworthy information at the top of your press release. You want to grab a journalist's attention by convincing him or her that your story is interesting. Thus, put what you feel is most compelling about your book at the top of the release. For nonfiction writers this may include your area of expertise. Your press release should be written in AP Style, a standardized way of writing used by most journalists.
Remember, your press release is not a book report; it's merely a snapshot of what you have to offer. It should be no longer than one page. Journalists are busy people and don't want to read your life story or a detailed description of your book when deciding whether or not to contact you.
You should send your press release to multiple media outlets. Try to find publications that cater to the subject matter in your book. While most authors have dreams of being on Oprah or having their book featured in The New York Times, it's usually better to build credibility with smaller publications first. Local media is a great place to gain initial press. Being a local author adds interest to your story. With the credibility built from being in smaller publications and local media, larger media outlets will be more likely to take notice of your story(remember, Oprah receives numerous suggestions for stories). Be sure to follow up with the publications that you feel will be most interested in your story.
You can also distribute your press release in person. A press release and a copy of your book can be a great ice breaker with local media and bookstore owners. Your press release can be used as a direct sales promotional piece.
While publicity can be hard work without a guarantee, don't shy away from it. PR leads to the most convincing publicity that you can find.