First job interview experiences

So today I had my first professional job interview for a temporary HR Assistant position. It was most definitely a memorable one. And even though I was a mess, I got hired. When I fist got there the interviewer shook my hand and led the way to a small office where a lady was sitting in and there were two empty chairs(so i thought I would get interviewed by two people). so the lady says hi and i go and shake her hand and she introduces herself and then I sit down and she's just staring at me like I'm crazy. and then the man says "we are actually going down here" and points to the office on the other side of the hallway. I was like OMG, i was so embarrassed, so i just told the lady i'm sorry and got up. That mistake just made even more nervous than what i was so when he was asking questions I felt like my answers weren't even making sense and there were a lot of pauses, I just wanted it to be over already. When it finally was, he gave me his business card and as i was leaving, i dropped it without noticing, so he was going after me saying "hey you dropped my card." I seriously think they just hired me because I had a great GPA, which was the first thing he noticed from my resume.

How have you guys' interviews gone? Any tips on how to be calm?

yeah try to learn as much of the company and how it works so you can take control of the interview yourself and shape it to where you want it to go. Ask the person interview you questions now and then and answer stuff how they did using what they told you in your questions. Really try not to think of it as an interview