Turn off the AC and unplug it or switch off the circuit breaker
Remove and clean the air filter
Vacuum dust from the vents and return grilles
Open the indoor unit cover and wipe dust from accessible parts
Clean the evaporator coils with a coil cleaner if needed
Clear the condensate drain line
Clean the outdoor condenser unit
Remove leaves, dirt, and debris around the outdoor unit
Straighten bent fins carefully with a fin comb
Reinstall the filter and cover
Turn the AC back on and check for proper airflow
Schedule professional servicing if the unit is heavily dirty or not cooling properly