Hi Grendel,
I have only had one tandem so far so I can only give you so much advice. From my experience all I can say is don't think about actually jumping out of the airplane too much. That's what I did and I made myself really nervous. The tandem masters will make you feel as comfortable as they can and remember all tandem masters are professionals. If your like me once you actually get out of the airplane you are going to feel something you have never felt before, pure freedom!! Have fun!!