First Flight - What should I know?

Salutations All,

After years of playing in Microsoft Flight Simulator/X-Plane, reading
the rec.aviation newsgroups, and staring longingly out the window of
Southwest Airlines 737's whenever I go on business trips, I've finally
swallowed hard and taken the plunge - my first introductory flight is
this Saturday with Skyline Aeronautics out of Spirit of St. Louis
Airport (KSUS) in St. Louis, MO. The scheduler said I'm scheduled in a
Diamond Katana two-seater, tail number 227RD.

Obviously, I'm nervous and excited about my first time up, but what
things should I know? Is there really anything, or should I just show
up expecting a good, relaxing time? I'm a software engineer, so most
things in my business require a lot of upfront planning, reading, and
work. Is there anything I should make myself familiar with? Questions I
should ask when I get there, etc?

Any advice anyone could give would be most appreciated!

Regards,
Bryan Porter