1. Avoid preheating Most modern ovens are so well insulated that preheating isn't as necessary as it used to be. Unless you are baking bread or something very heat sensitive like soufflés, you can generally skip the preheating step, or only preheat for a few minutes.
2. No oven peeking Once food is in the oven, don't open the door. Each time you peek, you risk leaking as much as 50 degrees of heat. Use the oven light instead.
3. Use the right burner for your pan The coil of an electric burner should not extend beyond the bottom of your pan. Flames from a gas burner should not lick the sides of a pot. If these things are happening, you are using more energy than necessary for the pan you are using.
4. Put a lid on it Covering food and liquids greatly decreases cooking time.
5. Turn it off early The residual heat in a pot, pan or baking dish will continue to cook food for quite awhile after the oven or burner has been shut off.
6. Cut veggies and meat small Smaller chunks of food cook much faster than larger ones. Added benefit is greater total surface area to coat in sauces.
7. Try one-pot cooking You'll save energy at the stove and in dishwashing by cooking one pot meals like stews, pastas and rice dishes.
8. All at once Practice cooking several meals at once in your oven and freezing them for later. Even easier is doubling a dish you're already making and freezing half for later.
9. Defrost Let frozen foods defrost completely in the refrigerator before reheating. This saves heating time on the stove or in the oven and prevents the need for firing up the microwave to defrost food.
10. Avoid the oven When reheating leftovers, you'll use much less energy by using the stove or a toaster oven.