Sufficient air flow! It is absolutely critical that the air flow through your return and supply ducts is unrestricted. Dirty air filters, clogged evaporator and condenser coils, fallen insulation, crushed duct lines, or an undersized duct system will not only adversely affect the temperature in your home, but I will also cause your system to work harder and wear out sooner. As a result, not only will you see an increase in your monthly utility bills, but a call to your local service company is not far behind.
-Make sure you regularly check your filter(s), at least every 30 days. Replace them when needed.
-You can clean the condensing coils outside by hosing them off with water. Not too hard of a spray stream though or you will damage the fins. Be careful mowing the lawn and try to keep from slinging cut grass and dirt onto the outside coil.
-If you are inclined, you can wash your evaporator coil inside by using a solution of dish detergent and water. Use a brush and go in the direction of the fins as to not cause damage to them.
-Be careful crawling around in your crawl space or attic. You do not want to crush any of the ducts.
-You can always call your local service company. They will most likely sell service agreements to come check your system out at least twice a year and clean the coils for you as well as performing other preventative maintenance items. Most of the companies will have other added benefits for loyal service agreement customers. Shop around and find out who is offering the best deal by comparing benefits and the services they offer. Ask friends and neighbors who they use. Having a service agreement is a wise investment to protect your HVAC system.