It is a good idea to have the furnace cleaned and change the furnace filter plus, consider a new furnace if the one now is not energy efficient. The savings will pay for itself in no time flat and will improve the value of your home as well.
Low-income households can qualify for many different government and state weatherization programs.
Adding more insulation around window frames, walls, attics, pipes and even the water heater can bring even greater savings. A plumber can really be of help in those things. They are familiar with pipes and water heaters.
Running the ceiling fan in reverse can make a room much warmer, I do this in my kitchen and dining room and it helps in circulating the hot air downwards.
Doing such simple things can make the home feel warmer and cost less to heat. It is never too late to winterize instead of letting your money simply, go out the window.