And don't forget the easy things. The U.S. Dept. of Energy reminds us to clean air filters and registers. And try not to use your kitchen and bath ventilating fans. In just one hour they can draw all of the heated air out of a home. Your ceiling fans can also be a help.
Hot air rises.
In a house with high ceilings that can mean that all the hot air is just hanging around over your head. A ceiling fan set on low can circulate the warmer air. A final consideration is to make sure that your home has proper weather-stripping. All those gaps around your doors and windows can add up. In fact, a typical home that hasn't been weather-stripped is like having a window wide open all winter.