Hmm. If it is not officially sanctioned by a major car club (such as SCCA), I would check the course out EXTRA carefully to make sure there aren't any danger areas where an off-course excursion may break something or injure someone. You may think 65 mph isn't all that fast, but trust me, it's plenty fast to bend metal and then some.
Otherwise,
Goomba had it pretty well covered. If it is your first time, just concentrate on remembering the course. Most newbies are very surprised at how quickly everything happens... even in 2nd gear. Your priority should be to 1-remember where you're going and 2-drive smoothly and begin learning how your car behaves at 10/10ths.
Do: Take a folding chair, some food, a lot of water and a good tire pressure gauge. An umbrella is handy in the summer. Dress comfortably, but in long sleeves. When you walk the course, remember any areas that may be rough or covered with sand or loose grit as old asphalt or concrete may have a lot of debris on the surface.
Don't: Spend too much time socializing or you will not get to walk the course and commit it to memory. Don't show up hungover from partying too much the night before (

ask me how I know) Don't try to over-drive the car the first time out. Accept that you will be slow. Speed will come with time.
Car prep: Tech your own car. Make sure the battery is secure. Make sure your brakes are in good shape and don't need to be bled. Ask others have already indicated, remove all loose items from your car. Check under the seats --you'd be surprised at the junk that can get stuck under them. Over inflate your tires by 5-10 psi. to reduce tread deformation.
That's about it. Go have fun.
BTW, that pyramid of speed thing is just some guy stroking his own ego. Funny but I wouldn't think too much of it. What he
neglects to mention is professional drivers trump anyone who goes racing on his own dime. At the very top of the racing heap is
someone who is paid to race.
M