Some advice a recruiter gave me once: Imagine you're an actor playing a part, rather than a job candidate. Also, if you're asked a question but draw a blank on an answer, you can try to clarify the question a bit - this gives you a little time to think, plus you'll be sure you're correctly interpreting and answering the question.
This same recruiter presented me to a company where I was interviewed by six people at once... and I tripped over an easel on my way into the conference room
But I still got the job.
Good luck tomorrow!
