Interviews can be rehearsed so its a little easier actually. There are lists of the most commonly asked questions that you can memorize little soundbites and key words to. Try googling some resources. Try rehearsing good eye contact that isn't too intense. It's also ok to pause and consider an answer to a question whereas usually in other situations it would be awkward. If you really can't think of an answer, just say something like, "I'll have to give that some thought and get back to you on that matter/point etc."

I know this was posted two months ago, but I thought I'd reply anyway...