Oven:

• Don't peek!
  Every time you open the oven door while cooking, you lose 25° to 50° F of oven temperature, which makes you waste more electricity or gas. If you can, use the oven light to check on your food.

Microwave:

• Zap it instead!
  Microwave ovens use about the same amount of power as conventional oven, but they work much faster. Use them for reheating and for small items. They are less efficient when cooking large dishes.

Stove:

• The cleaner, the better.
  The cleaner your burner reflectors are, the better they work. Good quality, clean reflectors can save up to 1/3 the energy used by the stove. Also, some ovens have a "self-cleaning" feature; if yours does, use it right after you finish cooking to save energy.