However, let's get this clear: We can't correlate sales with interviews (except possibly if you are a guest on the top TV shows). Think of being interviewed as one more way to get your name known, which leads to book sales. Focus on the cumulative effect.
Probably the best way to break in occurs when your publisher sets up interviews for radio and TV. If they think your book has "legs," they'll do what they can for you. They may even hire a publicist. But for most of us, it's a do-it-yourself project.
Too many writers fail to realize that successful publishers put out 100-plus books every year. The obvious big-name writers will sell their books and hit the best-seller lists, and publishers put their advertising dollars behind obvious winners. You have to prove your sales record to get them behind you.
These days, publishers rarely pay expenses for authors to go on book tours. Gone are the days when most TV stations paid authors' travel expenses. (Some of them still pay your expenses once you land in the city, by providing a hotel, but that number continues to decline.)
For you to be interviewed
means you do what you can to promote your book.