Don’t Peek
Most oven doors have a window that allows you to see your dish while it is cooking. If for some reason yours is cloudy, or you can’t see your dish, never open the oven door. Every time you open the oven you reduce the temperature inside, which can have a negative effect on how your dish turns out.
Opening your oven lets heat escape and it also allows cool air into your cooking space, and you don’t want that. When there are inconsistencies in the temperature, your baked goods won’t cook evenly. Unless the recipe calls for the door to be opened, like with a cheesecake, let it be until the timer goes off.