The biggest mistake I made was not bringing my own helmet. I wore some crappy ass helmet that I'm sure hundreds of people already wore. It was sweaty and dirty to the bone with no padding left in it. I got some nice rash right on my forehead the very next day. Luckily for me, my class was split over 2 weekends and I was able to go out and get a helmet that week in between.

Buy a Scorpion.  Everyone else in my class did.