Make sure the weatherstripping on all doors and windows is in good standing, and repair where needed.
 

Make sure all garage floor or driveway drains are flowing properly.
 

Inspect roof for loose or missing shingles, and check flashing seals; repair as needed.
 

Re-seal/re-stain any decks, fences, or other structures made of pressure-treated wood.
 

Clean out your gutters of any fallen leaves or debris.
 

Trim and prune bushes, trees, and shrubs - with the exception of those that flower in Spring.
 

If you have a wood burning chimney, check your furnace every year; if it is gas-running, every 5 years will suffice.
 

Check damper in fireplace for obstructions, such as birds' nests.
 

Drain off sediment from hot water tank and steam heating system.