Wet all of the concrete that you are going to trim with the grinder. This will lessen the amount of dust.
Grind down the rough edges along the side of the patio that are caused by concrete seeping under the frame. Grind this down by slowly moving the grinder over the area with the sharp edges. Continue this process until all of the burrs and spikes are removed.
Grind down the the top edges of the patio that are closest to the walking surface. Simply run the grinder down the edge and put a small rounded bevel across the edge. This will lessen the danger of cuts from a sharp corner.
Rinse the deck off with water when you are finished. This will remove any dust and debris from the patio surface.