How should I pack a cooler to keep things cold the longest?

Prechill the cooler and everything going in it, then pack as tight as possible, filling every air gap with ice. Air pockets let warm air circulate and melt ice faster. Start with a cold cooler, chill your drinks and food first, then pack dense with cans snug against each other and loose ice in every crack. For long trips, use block ice or frozen water jugs, keep the cooler out of direct sun, and don’t drain the cold water until you’re done.