Other than changing the filters of course.
A good visual inspection of the coils,wiring, and heat exchanger is a good start and light cleaning as needed. Also secure any copper refrigerant lines that may vibrate or rub on anything that would cause a potential refrigerant leak. Also make sure your thermostat is level.
clean your condenser coil pop the lid with power off back flush the condenser coil oil your motors should be a little oil port other than that you need gauges and refrigerant and a licence hope this helps
