Turn the power knob to the "off" position. Plug the air compressor in, if it is electric.
Push the air hose into the housing until you hear it "click" into place. Make sure the pressure knob is turned to the lowest pressure.
Turn the air compressor on. Aim the air hose at the deck surface, starting at one end of the deck and working toward the other. Blow off the leaves and debris in front of you as you move down the deck.
Continue until you reach the other end of the deck and all the surface debris is gone. If the power is not high enough, slowly increase it until the air comes out with enough force to remove the debris.
Insert the nozzle of the air hose between the deck planks, if they are spaced. Blow out any leaves or twigs stuck between the planks. Turn the compressor off.