If you start keeping records from the beginning, you will be able to establish trends, find your weaknesses, and improve your performance. Although you can buy food and drink at the concession stand, the track can be a hellish environment especially during mid summer. I have raced when the afternoon temperature was 105 degrees in the shade and spectators passed out from the heat. The pits and staging lanes are notorious for lack of shade. You will get dehydrated so have lots of sports thirst quencher type drinks.
Clothing often surprises wannabes.
Tank tops and shorts are out for the driver. Although the protection of a pair of blue jeans doesn't seem like much, if there is a fire, it doesn't take long for exposed flesh to get burned. The protection of jeans can give a few precious seconds of protection, enough to get away from a dangerous situation. Of course, the driver can change clothes between rounds. At one race I saw a pretty female driver wear a two piece bathing suit to beat the heat.