Congratulations on getting the interview to begin with! Don't forget that this in and of itself is a great step...and tells you that you already have the qualities that the company you are hoping to work for wants!
Here are a couple of other coping skills to help get you through the process with the least amount of anxiety.
*Envision a good outcome! When the anxious thoughts combat them with positive mantras and imagining everything going extremely well at your interview. Picturing yourself as confident, professional and engaging will go a long way in ensuring that it is so!
*Be prepared. Know exactly where you are going and give yourself extra time to get ready and get there so that you are relaxed and not rushed when you arrive. Look up online a list of typical interview questions that most employers use during an interview, so you can be ready with a thoughtful answer rather than be put on the spot. Have your resume/paperwork together and in a convenient spot ready to go the night before. Get a good night's sleep and a good breakfast the morning of.
*If you do get caught off guard by a question posed to you, don't be afraid to give yourself some time to answer thoughtfully, rather than saying 'I don't know', or just blurting something unintended out. I used to get thrown off guard by this as I like to process things before giving my response. I learned to say 'That is a good question, let me think about
that a moment.' This gave me a little time to get my thoughts in order.
Finally, be confident in yourself and your abilities! This will impress your interviewer and may even help to put them at ease...allowing the whole flow of the conversation to go really well.
Best wishes, and let us know how it goes okay?