If you plan on visiting several places, you can stop and shop as needed. If you use a cooler, you should also remember to make regular stops for ice to keep things cool. Keep perishables to a minimum. If you're really roughing it out in the woods and bears are around, be sure to follow park guidelines for storing food away from the tent or camper, and preferably high in a tree. Animals have very keen noses and can smell food from a long way off.
Every good camper knows that littering is bad.
You always take out what you bring in to any campsite, including every piece of trash. Bring garbage bags with you to help tote trash out of the camp. If you plan on cooking your meals, you're going to need some form of fuel, whether it's sticks and logs or charcoal and a grill. Pack accordingly, and don't forget the matches. Don't forget to bring items, such as a pot or pan, to cook in, along with a few utensils.