Also check caulking/weather stripping for gaps/cracks/aging
Insulation In / On
Attic hatch
Attic over living areas ceilings
Basement under living area floors
Crawl spaces (seal air leaks/prevent moisture)
Floors in rooms over an unheated garage
Foundation walls in basements
Knee walls in attics
Walls (check for inadequate or settled insulation)
Also check for a vapor barrier behind attic insulation to prevent insulation-robbing moisture, also consider replacing old doors and windows with newer, high-performance ones
Heating / Cooling Equipment
Install heat traps on a water heater tank
Insulate furnace ducts
Insulate water heater and hot water pipes
Programmable thermostats
Also consider replacing older central heating, air conditioning and water heating units with newer, energy-efficient models
Lighting
Replace halogen bulbs with other types
Use compact fluorescent bulbs
Use smaller wattage bulbs where possible
Also consider replacing ceiling fixtures with new technology, fluorescent models