Freeze a case of bottled water.
Thoroughly chill all food that will be placed in cooler.
Line bottom of the cooler with frozen water bottles.
Place chilled food on top of water bottles.
Fill gallon-sized Ziplock bags with ice cubes.
Pack the ice bags around the chilled food. Depending upon the length of your trip, you might need to replenish the bagged ice with a fresh supply.
Keep cooler in a cool and shady location.
Reserve a campsite with electricity.
Bring a plug-in cooler or a small refrigerator with you.
Plug refrigerator into the electrical outlet using a heavy-duty extension cord that is suitable for outdoor use.
Store food in the refrigerator unit.