Job  interviews are always stressful - even for job seekers who have gone on  countless interviews. The best way to reduce the stress is to be prepared. Take  the time to review the "standard" interview questions you will most likely be  asked. Also review sample answers to these typical interview questions.  
Then take the time to research the company. That way you'll be ready with  knowledgeable answers for the job interview questions that specifically relate  to the company you are interviewing with.