General tips
Oven Tips : With conventional ovens, minimize the preheating time. Unless you're baking breads or pastries, you may not even need to preheat.
Buying an Oven : In gas appliances, look for blue flames; yellow flames indicate the gas is burning inefficiently and an adjustment may be needed. Consult your manufacturer or your local utility.
Oven Tips : If you don't have one, consider buying a self-cleaning oven. They use less energy for normal cooking because of higher insulation levels. They also save on your rubber glove and cleanser purchases! However, if you use the self-cleaning feature more than once a month, you'll end up using more energy than you saved. When you clean the oven, do it right after cooking to take advantage of residual heat.