Prepare a list of items that you need to pack. Keep it in a safe spot or on your computer. Edit it after every camping trip to note which items you didn't use so you'll remember what you don't need to pack next time.
Pack items with which you can multi-task. A small microwave can heat water for coffee, tea, boiled eggs and pasta as well as cook other foods quickly, reducing the need for a kettle and an oven. Store leftovers in freezer bags and freeze them while you have your electricity plugged in at campgrounds. You can reduce the need to buy ice to keep your food cold during your travels with the pre-frozen bags, and then thaw and eat the leftovers when you're ready.
Pack foodstuffs, linens and clothing in square plastic tubs that fit together on top of each other. Allow each family member to take only what items will fit in "their" tub. Keep the tubs in the car or on the floor of the camper, stacked on top of each other, while you travel and bring them into the camper in the evenings or after you have set up camp. Since you have the items stored in plastic containers, you can place them outside your camper, even in rainy weather, when you need more space in the camper.
Purchase foodstuffs along the road. You won't always find your favorite brand, but you can eat well without worrying about storing large food supplies.
Hang shoe organizers and other netting bags from the walls and along the ceiling of the camper. They will fold up with the camper when it folds down and will provide storage space while the pop-up stands upright.
