Bring an instructor FOR SURE as a start. Even basic traits such as seating position that the instructor may comment on makes a huge difference throughout the day.
Wear some smaller shoes or something so you don't get caught up with the pedals. Tennis shoes for example are great. Take all the junk out of your car. Including the floor mats. All the stuff rolling around can be very distracting and maybe even getting in the way...
Check all your fluids and tire pressure before going on track. Give your car at least one warm up lap at slower speeds and same for slowing down to let your brakes cool off. Don't use the handbrake when you park either.
Bring some Oil, other fluids (brake fluid etc), Air Pig for filling the tires, Tire pressure gauge, Windex and paper towel... Torque wrench and a jack just in case to look for something if the need be. Oh and don't forget water for yourself
Dunnville, Toronto Motorsports Park, Shannonville, and Mosports DDT are great places to start off. Have fun!