Visit the restroom before going on camera, and don't drink caffeine or a diuretic. Remember, a reporter is telling a story. They may be using your voice to tell it by quoting you, but it is their story. If you recognize the story they're trying to tell early on, you will be more effective in getting accurate information into the story, and less disappointed when they quote you on what seems to you to be a minor matter, ignoring the rest of your interview and the points you were trying to make. Even when the reporter is writing a question and answer interview, it is still their story.
Reporters like to attribute information to reliable sources.
If you can give them a name and phone number, they'll be ecstatic, since reporters like to tell stories using quotes from several people. Before you begin the interview, ask the reporter to verify all of your quotes with you before they appear in print. Be very careful what you say, and try to avoid saying anything that could be misinterpreted. Keep it simple. Sound bites work well because they are less likely to be misreported and make good quotes.