Obvious we know, but turning the thermostat down by just 2 degrees will save you money. Wear a sweater and use fans to circulate the warm air.
Weather proof by caulking gaps, use draught stoppers.
Turn off appliances you are not using.
Clean the coils on the back of your fridge, lint filter and the filters on your furnace to ensure maximum efficiency.
Buy a dishwasher, a dishwasher uses less water than hand washing and if you only use it when it's full, the dishwasher will be more efficient as you will be heating less water to do more dishes.