Having had quite a few interviews I understand your nerves. One thing that will help with your confidence is how you sit in the chair. If its a crappy soft chair (they always seem to be) and you feel like a 7 year old cause you sink down, try scootching up and sitting further towards the front. That way you can keep your back a bit more straight. That does two things, it helps you breathe easier and gives you a more confident body posture. Oh, and at the end of the interview always give 'em a wink and a click while pointing with your double "air" six shooters. Okay, maybe not the last part . Good luck.