Inspect/Replace the HVAC filter
It is advisable to change the air conditioning filters every three months to maintain the air quality inside your home and maximize the efficiency of your system. So it's a good idea to buy and keep several filters, so you always have one on hand when you need it—for families with pets or allergies in one of its members, making the change more frequently will be convenient.
Clean Kitchen Sink Disposal
There are many ways to do this, but vinegar ice cubes seem to be the handiest and best all-around solution. Put some vinegar in an ice tray and let it freeze, then run the ice cubes through the disposal. It freshens it, but as a bonus, ice sharpens the blades.
Clean Range Hood Filters
You can use a degreaser mixed with hot water. Let the filter sit for a few minutes, rinse it off, and you're good to go.
Inspect your Fire Extinguisher(s)
This inspection doesn't require much: ensure it has easy access (not being blocked by a garbage can or anything else), that the gauge shows adequate pressure, and that it has no visible signs of wear and tear.
Test Smoke/Carbon Dioxide Detectors
Another simple task; your sensors should have a "test" button. If the alarm sounds, you're good to go. If not, replace batteries immediately and test again. If it still doesn't display, it's possible there's simply corrosion on the battery terminal, and it won't detect new batteries. Clean it and try again. If it still doesn't work, you'll likely need a new detector.
Run Water and Flush Toilets in Unused Spaces.
This mainly applies to guest bathrooms or any other sinks/water sources you don't use regularly. The idea is to prevent grime or any further buildup, and periodically running a little bit of water through will prevent this.
Test Garage Door Auto-reverse Feature
Since 1993 federal law requires all garage doors to have this feature after multiple child deaths. Test every month by placing a 2×4 on the ground where the door would close. It should reverse after a second or so when the door hits the wood. Also, test the photo-electric sensors if you have them by placing something in front of them (not your body). If the door doesn't immediately go back up, you have a problem.