Kitchen -

Clean the garbage disposal - cut the power, wipe the grinding chamber & flush, deodorize with ice and vinegar.

Clean out the oven - almost 10% of house fires are caused by unclean ovens and rangetops.

Check for expired fire extinguisher tags - make sure you are safe with up-to-date equipment.

Living Room & Bedrooms - 

Clean carptets, rugs, curtains and window ledges - remove any dust or mites that have made a home during winter.

Upgrade indoor lights - brighten up the area with energy efficient LEDs'.

Wipe down ceiling fan blades - major collection area for dust

Basements -

Install water leak detectors - water follows the path of least resistance, often into basements.

Check foundation for cracks and fissures - find early and address, can cause major problems later on.

Apply Drylok or other water sealer - to block walls and other masonry.

Install radon detectors - radioactive gas that can leak into basements.

Bathrooms - 

Clear out medicine cabinets - dispose properly of old medications

Recaulk tub and toilets - ensure water damage stays away from structures behind walls.

Deep clean with mold killing cleaner - ensure all mold spores are cleaned with a dedicated all-purpose cleaner.