Each brand of dehumidifier has its own specific instructions for cleaning in its manual. Still, the process usually starts with turning it off and then unplugging the unit to prevent a shock. Your next step is to use a slightly damp cloth to wipe the air vents clean of dust and dirt. You should then remove the tank, empty it and wipe it out with a bit of soap and water and rinse. Let the parts air dry completely before replacing them.