Choosing the Right Appliance For the Job
You can save energy simply by getting in the habit of cooking with the most efficient appliance possible for the food you are preparing.
In general, the higher on the following list, the less energy the appliance will cost you:
Slow Cookers ("crockpots")
Electric Convection Oven
So, lets say you want to reheat some leftovers for lunch. You could pop it in your big, hulking oven, but it would be cheaper to use the toaster oven. It would be cheapest to heat it in the microwave. But be reasonable. You're not going to make pancakes in your crockpot, so fire up that electric frying pan with impunity. And I know the Thanksgiving turkey won't fit in most toaster ovens.
These energy savings are not something to sneeze at. For example, using a microwave will reduce your energy consumption by about two-thirds compared to using a regular oven.
Perhaps the greatest innovation of the '70's was a great appliance to cook soups and stews that need to simmer for a long time. Yes, I'm talking about the crockpot. (Points off for those of you who guessed Leisure Suits were the discovery.)
Finally, you know how Asian cuisines always emphasize steaming vegetables instead of boiling them? You use a lot less energy steaming vegetables over a little bit of water compared to boiling them in a whole pot of water (some of us think they taste better that way, too). Or try microwaving them in a covered bowl with a little water in the bottom, to get the same effect using less time and less energy.