Change your Filter(s) Regularly - At least with every time change (twice a year) change your air filter. Keep a stock of filters on hand. Purchase them when on sale. Plugged filters are a major cause of furnace / blower failure and are a potential hazzard.
Keep your Air Conditioning Condenser clean- At least twice a season and more often in a dirty/dusty environment, rinse your outside condenser unit with a hose using a spray nozzle. Keep it free of leaves, weeds, and other debris. A dirty condenser makes your compressor work harder, reduces operating efficiency and in extreme situations can lead to compressor failure. When doing yard work check the unit for debris, etc.