What is the best way to store and reheat leftovers?

The critical variable is how fast food gets through the temperature danger zone between 40 and 140 degrees Fahrenheit. A large pot of soup left on the counter or put into the fridge as a single deep container can hold its center in that range for hours while the outside cools, which is exactly the condition bacteria need. Divide hot food into shallow containers no more than about two inches deep, leave lids ajar until it stops steaming so trapped heat can escape, and get everything refrigerated within two hours of cooking, or one hour if the room is above 90 degrees. Ice baths and stirring speed cooling for large batches.

Reheating has its own requirements. Bring leftovers to 165 degrees throughout, and use a thermometer rather than judging by steam, since microwaves heat unevenly and produce hot edges around a cold center where bacteria survive comfortably. Stir midway, cover to trap steam, and let food stand a minute or two afterward so the temperature equalizes. Rice deserves special mention because Bacillus cereus spores survive cooking and produce toxins if cooked rice cools slowly and sits, so refrigerate rice promptly and do not leave it out overnight. Label containers with dates, since the three-to-four-day refrigerator window is only useful if you know when day one was, and freeze anything you will not eat in that time rather than gambling on day five.