For this old house, two (relatively) simple steps will make a difference in our utility bills. The easy one first – replace the old programmable thermostat. The display is just about gone – we can set the temperature but not program it to go down at night.
The other step is to add insulation to the attic. Like most old houses, we have the yellow fiberglass stuff. And the R value is certainly below what is recommended for the DC area (which is 49). Fortunately there are quite a few options for increasing the coziness level; lots of useful information can be found on this site.