Thermostats are the controls that tell your heating and cooling equipment when to turn on and off. Slight changes to their settings can mean some of the quickest and easiest savings to be found in many homes. As a rule of thumb, you can save about 2 or more percent of your heating costs for every degree you reduce your temperature. So you'd save about 4 or more percent by going from 72 to 70°F. Likewise, raising the thermostat setting in summer will also save energy.
If you have a heat pump with electric back-up heat, the recommendations are slightly different. Most heat pumps use electric resistance strips (called the emergency back-up) to produce heat when the outdoor temperature drops below the home’s thermal balance point or about 35 to 40 degrees or when the thermostat senses a two or three degree difference between its setting and the indoor temperature. Electric resistance heat is expensive, so forcing the strips to come on to bring the house back up to temperature in the morning may defeat the goal of saving money. Therefore, for heat pumps with electric resistance back-up, it's best to set the heat pumps to the lowest comfortable setting and leave it there. Heat pumps backed up with gas do not have this concern.
In the summer, keep the setting as high as possible by dressing in light-weight clothing and using fans to stir the air to make occupants feel cooler.
Clock thermostats are readily available in home improvement stores and usually don't require much more than a screwdriver to install. They'll produce more savings if you program them to set the temperature back if you are out of the home at predictable times each day.