Before you bake something, your oven needs to be heated to the proper temperature. While it takes only a few seconds to turn on your oven, it can take several minutes for your oven to reach the right temperature. This is why it's often best to start the oven during the beginning or middle of your cooking, instead of waiting until the end. That way, the food will be ready faster.
Open the oven and check inside to see that nothing else is in there. Remove anything you find so it won't be getting reheated or possibly damaged. Some things often left in ovens are baking trays and leftover dishes, especially if teenagers live in the house!
Rearrange the shelf levels. Put the oven shelves into the position that you need them to be in for the cooking before the oven gets hot.
Check the preheat level required by your recipe. Turn on the oven according to the manufacturer's instructions and set it to the correct temperature.
Wait until the oven reaches this temperature before placing food in. Most modern ovens have a setting that lets you either see the current temperature or beeps when ready. If you have an old style oven, the best bet is to wait 15 minutes to allow the oven to be fully heated.
If the temperature gauge of your oven does not work, or works improperly, you can purchase an after-market one from your local hardware store that just hangs inside the oven.
For older-style ovens, place the item in the oven and extend the cooking time by approximately 10 minutes.
Make sure you close the oven door properly. Some ovens have doors in the same style of a car, and it can be hard to tell if they're closed completely.
If you don't wait until oven is fully preheated, food can take longer to cook, or cook unevenly.
Don't open the oven door, just to check. You lose a lot of heat every time you open it, which means your food will take longer to cook.