Usually, for a pre-determined fee, the contractor who installed your system or another qualified service technician will come to your home and inspect your system. He or she will check the refrigerant, inspect and oil fans, and make sure that wiring and switches are operating properly. The fee will increase if the system needs repairs, refrigerant, filters, or if the ducts need cleaning.
Many contractors now offer service contracts under which they will inspect and service your cooling equipment once a year and provide emergency repair service when or if it is needed. Before purchasing a service contract, be sure to weigh its cost and coverage against the cost and likelihood of future repairs. If your system is new, it probably comes with a warranty, which is included in the purchase price of the system. If you sign a service contract, be sure that it spells out what parts and service are provided and that it doesn't duplicate coverage you already have under the warranty. Because service contracts vary significantly in coverage, compare the coverage offered by several different companies.
You may do some of the maintenance work on your own. If your system has disposable filters, check them every two months and replace when necessary. Clean permanent filters as directed by the manufacturer, and make cleaning duct outlets and registers a part of your regular housecleaning routine.