To calm your self down, I'm actually the person that is described in the book. I'm inherently nervous when someone questions me regardless of guilt, if you were to sit down with me and ask me questions that were harmless I would still get flustered (my face gets red and I can feel my heart pumping). What are some good techniques to calm yourself down, I know you state visualizing something calm but what other options have people used to calm down?  

I am the same way, I get nervous. So when I took my poly. I found a little dot on the wall and just stared at it. I tried not to think about anything. just keep your mind blank because the minute you start to think about something you will start thinking about everything and if you are doing a good job or not and that will make you fail. That is what they want you to do. Just do your breathing and think about nothing and as soon as you answer the question, don't think about it at all and I mean at all. Juat stare at that dot on the wall don't look around. That's what worked for me. good luck.

Don't worry--if you have nothing to hide you should do fine.  If you mess with your own head (it may already be too late to avoid that now), anything could happen.