Be sure to eat a little something before you exercise. Although there are many different opinions on the timing, in general you should be ok eating a light snack up to 60-minutes prior to your class. This helps regulate your blood sugar and avoids any distracting hunger pangs. Popular snacks can include yogurts, bananas, fresh fruit, energy bars, peanut butter sandwiches, etc.
Drink, drink, drink! The key to a healthy body is staying hydrated. So be sure to have water before, during, and after your ride.