1. Be prepared. Anticipate any kind of question you may be asked. Anticipate your answer. You can find some sample interview questions on the internet.
2. Practice. If the interview is in your first or second or third language you need to practice to yourself or another to sound smooth and confident in the interview. This will also help you feel more relaxed during in the interview.
I've been on many hiring committees in the education field. I agree with the other person that you should bring or state specific example answers to the questions. Also - never say "I don't know" . If the question is in regards to something you haven't experienced and they expect an answer you can say how you "would" handle the situation or you "would" do the job etc. Don't ever end with just I don't know. Also, do research on the school, job, company, position etc. Casually bring it up at some point in interview. That way they know that you took the time to learn about the school/job.