For some things like refrigerators, the energy cost over its lifetime can exceed the initial purchase price, so the one with the lower sticker price can easily be a trap costing much more in the end. If you are selfish you will only pay attention to the dollar cost to you. Strategic decisions usually have greater impact than tactical decisions. Living near where you work, biking, walking, and telecommuting will have a larger effect on energy consumption than purchasing a more fuel-efficient car, which in turn has a larger effect than checking the tire pressure and tuning the engine. Space heating, water heating, and refrigeration are usually the biggest energy consumers in the home.
Lighting is usually more significant in offices.
Weatherstrip and insulate to stop heat loss. Dress for the season instead of trying to maintain a tropical climate in the middle of winter or a polar climate in the heat of summer. At night, a quilt keeps you warm without requiring heating all the air of all the rest of the house. Small lights close to the task at hand are much more efficient than a high-powered light fixed to the ceiling. Fluorescent lights consume much less energy than incandescent unless the light is only on for very short periods at a time.