COOL IT Wait to wrap up your sandwiches until all the ingredients have cooled off. Steam from hot items like toasted bread or warm meat will build up inside the plastic wrap and make the bread soggy.
LAST THINGS FIRST Place food in the cooler in the reverse order you plan to eat it, so you won't need to go searching. And you don't have to pack light: A fully packed cooler keeps everything colder for longer.
DRINKS ON THE SIDE Keep the sodas and beers in a separate cooler; a drinks cooler tends to be opened and closed frequently. Also remember to keep some ice in resealable bags so that it's clean for drinking.
TAKE COVER Keep your food in the shade, even if you're in the sun, and try not to leave sandwiches outside the cooler for more than an hour. Put any leftovers in the trash rather than take them home.
DRESS FOR SUCCESS If you're bringing a salad of mixed greens, pack the dressing separately and toss right before you eat. Heartier salads like ones made with green beans can be dressed ahead of time.