If you don't know an answer, say you'll find out and call back. Tell the reporter you will call back in 15 minutes or so. Collect your thoughts and then follow through on your promise to provide an interview. Have a message. Prepare a single communications objective and two or three secondary points you want to make, regardless of the questions you're asked.
Reporters often frame their questions to bring out the conflict in a story.
Anticipate the tough questions you may be asked and rehearse your answers. If they're not the questions you'd prefer to respond to, address them briefly and segue to what you want to say. Use simple language rather than technical terms, and try to speak in short sentences. Eight seconds is the average length of a TV sound bite. Be friendly, but don't be lulled into flippancy, sarcasm or forced humor.