Load your on-the-go fridge correctly and you’ll keep your sandwiches from getting soggy. 

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This article originally appeared on RealSimple.com.

It’s early in the morning, you’re working on your camping checklist or running through those pre-backyard party to-dos, you turn to the all-important cooler and realize: You have no idea how to pack a cooler. Sure, you could just toss all those drinks and road trip snacks and ice packs inside and hope for the best, but there has to be a better way, right?

Right. There is a better way—a way to pack a cooler that keeps everything inside cool and refreshing even after hours in the car or outdoors. Doing so may even allow you to fit more into the cooler, maximizing its cooling potential. (It’s a little like learning how to pack a suitcase in that regard.) Depending on what you’re keeping inside, it’s sometimes necessary to pack a cooler correctly: Meats, cheeses, and other perishables can reach unsafe temperatures if they’re not kept cool enough, and packing the cooler the right way can help keep them that way.

Taking the time to pack the cooler right will keep your food and drink more satisfying and cool; it can also keep you and your friends, family, and guests healthy, so there’s no reason to not do it. Learn how here, and enjoy chilled food and drink whenever and wherever you want it for years to come.

1. Match the container to the outing.

For one-day excursions that include a lot of walking, opt for a soft-sided cooler, which is light and easier to carry. It also lets you squeeze out air, which will help keep everything chilled, says Mike Daurio, store manager of REI in Chicago. Hard-sided containers typically have better insulation, making them good for longer trips, when food (especially perishables) needs to be kept cool for a few days. Choose a container that’s about two inches thick—the thicker the insulation, the better it cools. High-end brands, like Yeti and Pelican, offer soft-sided coolers that can manage longer trips; in the case of coolers, a higher price does tend to mean better chilling capabilities.

2. Maximize chill.

Aim for about a 2-to-1 ratio of ice or gel packs to product, says John Maldonado, director of product design at the cooler brand Igloo. Start freezing gel packs at least 24 hours in advance so you don’t leave pockets of liquid on the inside, which spurs melting, says Michael Pimpinella, a packing manager at HelloFresh in New York City. Fill plastic containers with water, freeze them, and pop out the slabs of ice. Or chill large water bottles, which can double as refreshing drinks later. Chill your cooler in a large fridge or freezer, or at least bring it inside—you don’t want to pack ice in a hot container.

3. Pack strategically.

Put large ice blocks on the bottom—they melt slowly and generate cold longest. Then add proteins and dairy. (For longer trips, pack proteins frozen; they act as bonus ice blocks and should thaw in a few days and be ready to cook.) Add more ice or gel packs, then drinks and items like guacamole and mustard, followed by another layer of ice. Top with soft items, such as sandwiches. The FDA advises keeping a thermometer in your cooler if storing perishables; food should be at or below 40 degrees Fahrenheit. Bringing drinks only? Fill the cooler with ice and a half cup of salt. “Salt water has a lower freezing point, and the cold water will touch the beverages at every point, whereas cubes leave pockets of air,” says Daurio.

4. Store it in the shade.

Keep your cooler as chilly as possible while en route. “It’s not always practical, but putting it in the air-conditioned car as opposed to the trunk should slow down ice melt,” says Maldonado. When you arrive, leave it in a shady spot. If trees aren’t around, don’t keep it in the car—on an 80-degree day, the temperature inside a car can reach nearly 110 degrees in just 20 minutes. Instead, bring it outside and throw a light-colored blanket or towel on top to keep the temperature from climbing. An emergency blanket (with the reflective side facing out) makes a handy shield too, says Daurio.

5. Slow down ice melt.

Once your cooler is firmly planted, keep the lid tightly shut and limit how often it’s opened. “A cooler’s worst enemy is changes in the air temperature inside, and opening it a lot will raise the temperature,” says Daurio. During one-day trips, resist the urge to pour out any melted ice—the water is actually an insulator that helps keep the remaining ice chilly, says Pimpinella. If you’re using the cooler for a few days, you can drain the water, but fill the extra space with new ice and gel packs. “Excess air can promote heat transfer and melt the remaining ice faster,” says Pimpinella. If you’re low on ice, fill gaps with newspaper or Bubble Wrap to help eliminate air pockets.

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