Bright Bulbs - Using a brighter bulb than a fixture can take can cause the bulb to burn out quicker and damage the fixture or even start a fire.
Messing Up Mirrors - Spraying an ammonia based cleaner directly on a mirror can harm it if even a drop gets around the frame. It can remove the reflective backing and cause a dark ring around the mirror.
Overpowered Range Hood - Follow the specifications for which size range hood you need for your range. Using a too powerful one can actually drawn in smoke in your fireplace or pull in other exhausts from your furnace or something else.
Plan Where You Plant - Make sure you know how the trees or other plants you plant in your yard grow. Putting a large tree near a driveway, the roots can destroy the pavement.
Problems with Pressure Washing - Too powerful pressure washing can actually damage siding and other things on and around your home.
Over-sized Air Conditioning - If it's too much for your home it might run short and improperly which can make the unit not last as long and use way more energy.
Mulching Mania - A little mulch goes a long way and a lot can smother roots of healthy plants.
Don't Mow Too Low - Mowing the grass too low not only can kill the grass, but it can let light shine more on the soil which encourages weeds to grow.