Taking the time to practice answering the interview questions you will probably be asked during a job interview will help give you a framework for your responses and will help calm your nerves, because you won't be scrambling for an answer while you're in the interview hot seat.
Practice interviewing with a friend or family member ahead of time and it will be much easier when you're actually in a job interview.
Review common job interview question and answers and think about how you will respond so you are prepared to answer.