#2 - Are the foundation, walls and ceiling in my home properly insulated?
Since home heating and cooling is the largest percentage of energy use for most homes, this has the potential for the largest energy savings. The 2006 International Energy Conservation Code (IECC 2006) recommends an insulation value of R-30 in the ceiling for homes in the southern U.S and R-49 for homes in northern climates. An R-49 is achieved with roughly 18 inches of insulation, depending on the insulation type. If you have less, consider adding more insulation.
In northern climates, other than ceiling insulation, basement and rim joist insulation could be one of the easiest ways to reduce heat loss and pay for itself in a year or two in savings.