Find someone reputable to do a service on it.
Open the indoor unit and check/ clean /tighten elec. connections, check amp draw on fan motor, check/ clean the evap coil and drain pan. Check proper flow on Secondary pan if you gave one.
Have them write down the fan motor capacitor numbers.
Check / clean the condensate drain for proper flow and no blockage . Replace the return air filter.
Check / clean the outdoor condenser coils, check /clean / tighten the elec. connections, check amp draw on condenser fan motor, write down capacitor numbers. Connect gauges and check/ adjust freon charge after cleaning and checks are done.
Extra credit:
Buy a nice Fluke meter like an 87v and learn how to use it when the HVAC goes down...
Find the manual for your model and read it.