Damien Mulley has published his tips for successful media interviews.
The most important thing about any interview is that you are prepared for it. If you put out a press release then you should already know your topic inside out. You should be expecting and be prepared for interviews well before the send button is pressed on that press release.
One thing I’d add to his list, is passion. You cannot replicate passion about the subject matter – it’s infectious.
Murphy's Law 