Unplug the fan
Remove the front grille or cover
Remove the rear grille if accessible
Take off the blades if the model allows
Vacuum loose dust from the grilles, blades, and motor area
Wipe the grilles and blades with a damp cloth
Use mild soap and water for stubborn dirt
Dry all parts completely
Clean the motor housing with a dry or slightly damp cloth
Reassemble the fan
Plug it back in and test it