Make sure that your home is well insulated. Have it inspected once every year, as many insulation companies offer free evaluation. If there are gaps in the insulation, your HVAC system will have to work harder. This will increase the amount of energy spent on heating or cooling. The extra strain on the unit will also increase the chances of HVAC repair needs.
You should also check for any gaps or cracks in the ductwork will adversely affect the efficiency of your HVAC unit. These openings can cause warm air from within your home to flow out and the conditioned air to move out of the duct. Again the unit will have to work harder and continuously to keep the indoors comfortable. So make sure that the ductwork is checked once every year or twice a year when the season changes.