One of the best things about going to the Writers of the Future workshop a few years back was when they brought in one of the country's leading PR guys. He taught us how to write a press release (see notes here).
He also taught us how to manage interviews. The single most important thing is, know what you want the interviewer to take back to their readers. Now, it may just be that you want to add to your public persona by just being the professional you and answering the questions in a straightforward manner. But in general, if you're having an interview it's probably because you have a book coming out or something of that nature.
If that's the case, you want to make sure that early in the interview, and preferably more than once, you get those details into play. This is called steering the question. So an answer to a question like "How about those Dodgers?" you might say "Well, in my new book, Cybermancy, I have a scene with Tisiphone and Cerice arguing their favorite baseball teams." The problem with that example is that it's: A. not true. B. heavy handed. C. not terribly funny. Still, it illustrates the point. There are things that you want to get into the transcript early and it's important to have them in your head from the get-go so that you can slide them in as appropriate and mostly more than once.
Beyond that, you should always remember that as an author you are public figure (possibly only semi-public but the difference is one of degree). What do you want your public persona to look like? Are you funny? Modest? Shy? Bombastic? Do you start fires or put them out? Unless you're a very good actor you want to keep these as close to the core you as you're comfortable with, but you do want to think about them and reinforce the face you want the world to see.
It's really just another type of storytelling and if you know that going in and keep it somewhere in your head, it'll make things easier.
Personally, I'm genuinely snarky and sarcastic and also utterly in love with writing. Fortunately, this is a good persona for a writer and I work to reinforce it in appearances. Lots of jokes, mostly at my own expense, but real intensity and love when I talk about writing.
How about you? Any tips or tricks? Violent disagreement with managing your persona? Thoughts on what you'd want an interviewer to take away from a conversation?