Turn off the power to the AC unit
Remove the front cover or access panel
Take out the air filter
Clean or replace the air filter
Vacuum dust and debris from the vents and interior
Clean the evaporator coils with a coil cleaner
Straighten bent coil fins with a fin comb
Clear debris from the outdoor condenser unit
Rinse the outdoor coils with a gentle stream of water
Clean the drain line and drain pan
Wipe down the fan blades and housing
Reassemble the unit
Restore power and test the AC unit