Because I tend to be gone for 8-12 hours of the day I tend to start a night or two before
Batteries: all my charged batteries get put in the left hand side of my vest or bag, any uncharged batteries are on the right so I know to charge them.
Cameras: Dial in my settings the night before if I know what track I'm going to be at, check for any large chunks of dust or oddities.
Lenses: Inspect all the lenses before I leave, make sure filters are attached and elements are clean.
Storage: Move my P3000 backups to the computer and back it all up, clear the device of any used space and leave it plugged in to charge overnight. Wipe all memory cards (format in camera) to be safe and test them with a few shots to make sure it's still good.
Misc - Put some rain sleeves in the bag (forgot this a few times), monopod and jackets in the trunk with a small cooler of snacks and some water bottles in the freezer and water/gatorade in the fridge (I hate paying $3 for a bottle of water at the track).
And of course, the most important part is make sure that I have my passes/tickets in my wallet or under my phone the night before so I can actually enter the event 