A general assignment reporter may have little to no background in your area of expertise. Be willing to provide background.
If you're appearing on television or radio, keep your sentences short and simple. Get to the point. You'll be "on-air" for, literally, a moment or less.
Expect a good number of questions. This person wants to understand your topic but may have no background in it. He must quickly acquire as much as he can.
Don't guess. If you don't know the answer to a question, there's nothing wrong with saying, "I don't know, but I'll find out and get back to you." Then, follow up and do that ASAP.
Nothing's "off the record." Don't say anything to a reporter that you're not willing to see in print.
For most of the feature and research stories which bring faculty and media together, there's no reason to be nervous. The reporter really wants to work with you. You have expertise or a story to share, and they have a product to get out.