Dust everything from floor to ceiling with an extended-handle duster (you may want to cover your hair and wear a dust mask). Suck up any remaining debris with a vacuum, using the extension hose and crevice tool for nooks and crannies. Then, sweep and vacuum the entire floor. Next, remove and hose down the window screens. With a sponge and hot, soapy water, wash the walls, sills, doors, and frames, and mop the floor. Wash exterior walls too. If the porch is really dirty, pressure-washing may be necessary.