Protect your investment by reading the following!
Roof Runoff. Maintain gutters and extend downspouts with black solid tubing five to ten or more feet away from the foundation. If the terrain permits you can bury the runoff tube for a nicer appearance. Dumping all that roof water on a "splashguard" simply allows the water to percolate thru the looser backfill increasing "seepage" and hydrostatic pressure on your foundation walls, both of which can lead to cracks and wet basements (and then possibly mold).
Drainage. Maintain positive drainage around the entire foundation, preferably achieving six inches of fall over ten feet. Fill in, re-grade and compact but don't let earth get closer than four to six inches from siding or wood. This is the single best thing you can do for keeping your foundation dry. A dry house is a happy house! Moisture is the ultimate source of much of a structure's problems. Additionally, make sure the sump pump & condensate pipes discharge well clear of the house or you are just recycling the water back down the foundation walls.
Ventilation. Assure the attic is properly ventilated and that insulation isn't blocking the soffit vents. Put a remote thermometer at mid height in the attic and watch it on a summer day. If the temperature goes above ~135° to 140° then you need better ventilation. If increasing passive ventilation isn't possible than consider installing mechanical or even powered vents. Good ventilation evacuates moisture buildup and preserves your wood structure, while keeping the heat down prolongs the life of your roof. You will also save on cooling costs. Open your windows when weather permits to refresh your indoor air, which, with today's tight homes and our extensive use of chemicals, can be somewhat polluted.
Thermostats. To save energy install a programmable thermostat. They cost from $40-$120 at the big boxes, are easy to install yourself, and will pay for themselves in no time in reduced energy bills. Program the heat back 2° at night if you have a heat pump with electric backup or 5° to 10° if you have a gas or oil furnace. If you turn a heat pump down too much they will kick into backup heat mode to catch up in the morning and this is costly IF the back up mode is electric resistance coils—not an issue if you have fuel back up.
Air Filters. Change your air filter every three months or so, depending on if you have animals or not and how clean you keep your house. Air filters are not just about cleaner (and healthier) air but they protect your furnace as well. A dirty filter will shorten the life of your heat exchanger ($$) as well as cause "short cycling" caused by insufficient airflow tripping the overheat sensor. In other words the furnace will constantly cycle on and off. For best value buy pleated filters. Avoid the cheap spun fiber type and the washables. If your budget allows, the more expensive "electrostatic" filters do work great—or better yet, retrofit an electronic air filter, which are as good as they get but do still require regular cleaning.
Furnace Servicing. Further extend your furnace's life by having a technician service it at least very two years (every year highly recommended for oil furnaces). He will check the all-important heat exchanger and safety sensors as well as the evaporative coils, which neither you nor the inspector can readily get to, and give the whole system a good cleaning and tune up. An annual contract is best to assure you actually get around to it, and usually involves less money in the end.
Appliance Venting. DO NOT, under any circumstances, vent your dryer or self-installed bath fans into the crawlspace or attic or into the house. Moisture must be vented to the outdoors or you will promote wood deterioration and mold in no time. Remember, moisture management is key to a happy house. Even though we humans prefer 30-50% humidity (45% is ideal) a house structure prefers 10-15%. Mold, by the way, requires spores, food and moisture. Good filtration reduces but does not eliminate spores. Food exists everywhere (carpets, drywall, wood, insulation backing) and can't be eliminated. Moisture control is where you fight your battle against mold. Use your bath fan for every shower.
Water Heater Flushing. Get longer life out of your water heater by flushing it regularly of corrosion causing sediments. Hook a garden hose to the spigot at the bottom, run it into a bucket or tub (so you can see just what comes out) and open the valve full way for 30 seconds (or more if sediment is still evident). Ideally do this once a quarter if on well water, or once a year if on public water. Also, every five years change out the "sacrificial anode"—it corrodes instead of your tank liner but after a while it's all used up! It's the sunken large hex nut on top and can be easily replaced if you are the least bit handy. (Max 125° on the water temperature setting to prevent scalding, especially if you have young children.)
Shower Water. Save yourself a long-term headache by managing the water in and out of your shower or tub now. Rotted floor corners and failing tile are a major pain to replace. Fix it now before it's a problem. Remove the bad grout, clean thoroughly with bleach and then isopropyl alcohol, and re-grout and seal. Same with caulking. Get a showerhead that extends way out to keep water off the front wall. Install a splashguard in the corner. Create a moisture proof seal at the base of the tub where it meets the floor (caulk both sides of the corner round.) Teach your kids how to seal the curtain or install sliding doors. Otherwise, tiles come loose and the walls, subfloor, and eventually the joists rot and weaken. Prevention now or $$$ later!
Smoke Detectors. Fire is the fourth largest accidental killer in the U.S. Smoke alarms cut your risk of dying in a fire nearly in half. Change the smoke detector batteries every year and test regularly. Watch those "handyman extension cords", frayed lamp cords, overloaded outlets and unattended cooking (#1 cause of house fires).