How to ace the most important interview of my life?

I have to appear for a corporate interview in a few days. And it's not that I'm not prepared for the general or technical questions (I'll obviously prepare those beforehand), it's the delivery I'm worried about. After a few mock interviews, I've noticed that during the first minute of the interview, I'll be a bit nervous, which is apparent from my voice and heartbeat, and as the conversation progresses and I get to speak more and hear the interviewer, I become calmer. So how do I not ruin or look nervous in the first question? Do I say sorry if I sound nervous I'm just really excited for this interview. Also, this is the single most important thing in my life Do you have any tips in what unique thing I can say to really impress the partner/manager of the firm? Since there will be many other candidates, I need to know how can I set myself apart, perhaps by asking an unusual question in the end?