One of the greenest ways to save on heat, is a warm sweater, yes by wearing a warm sweater. When you dress warm, you can keep your thermostat at the 60 something range, and feel nice and warm at the same time. This can save up to almost 20 percent on your energy bill.
Have ceiling fans, well they can help also with saving, just by flipping the little black switch, will help to circulate the warm air, since it will rise.
Remember those little gadgets grand mom used to knit and sat them at the bottom of the doors. Well don't laugh, they help to keep any drafts from coming in. Don't have one, roll up and towel and it will work just as well.