Tightening belts and examine them for proper wear, This can help you avoid a period of downtime, while your system is undergoing a costly repair due to a belt break.
Clear drain lines and checking drain pans quarterly is a must, to reduce any risk of water damage, under and around the unit.
Filters should be changed monthly and/or quarterly depending on the filter type you may be using.
Check the humidity levels in the home or office.
Check fan balance and clearance.
Check thermostat for proper operation.
Lubricate and inspect bearing for wear.
Check temperatures at supply and return for proper temperature increase/decrease.
Monitor proper refrigerant pressures and temperatures.
Check compressor and crankcase heater amps.
Tighten up all connections, as well as observe the condition of all wiring.
Cycle the system to check performance.
Check all vents.