Buy a programmable thermostat.
In the winter keep it a little lower (68 degrees) than you usually would and put on an extra sweater or in the evening use blankets and throws if you're sitting watching television. If you're going to be out for a while over-ride the temperature to lower it temporarily. Or program it to a lower temperature if you are regularly at work during the day. At night you won't need it to be as warm (use extra blankets).
In the summer, keep it 10 - 15 degrees higher during the day when you're at work (you don't want to turn it off because it will cost more to cool the house down if the outside temperature is high). Program it to start lowering the temperature an hour or so before you get home so that it reaches 78 degrees. Use ceiling fans.