Get ready for the holiday cooking marathon with a quick oven checkup. If your appliance has a self-cleaning function, avoid using it right before making a major meal, as it can throw off the temperature gauge. And make sure the digital reading matches the cavity's actual temp with a tried-and-true analog oven thermometer. If it's off by more than 5 degrees, manually reset the display so that they're in sync. If the gap is more than 35 degrees, call a pro—it may be time for a new oven.