Make sure you know the station!
Go online and MEMORIZE the names of every reporter and anchor and read their bios carefully. When you are introduced to them they will love it if you know something about them and can compliment them on a big story they aired.
The interviewer will want you to meet everyone and everyone will give an opinion as to whether you should be hired.
Be LIKEABLE, intelligent, friendly and open. A newsroom is close quarters and everyone will be watching carefully to see if you are the kind of person who can fit in. Even if you are nervous, do your best to come off as confident and down to earth.