Spray an older deck with a garden hose using a strong spray nozzle to remove leaves and loose debris.
Prepare a mixture of water and laundry detergent in a large bucket.
Scrub the deck using a long-handled, stiff bristled brush dipped in the soapy solution. Rinse with a garden hose as you go.
Allow the deck to dry for three or four days before applying the stain.
Sweep away all traces of dust and debris from the deck before proceeding.
Apply sealer to railings and ledges with a wide paintbrush. Brush the sealer on the deck boards, painting in the direction of the grain. Remove any excess material as you go with the edge of the paintbrush.
Apply sealer to cracks in the wood and between boards with a paintbrush, if possible.
Apply a second coat of sealer for a smoother finish, allowing the surface to dry thoroughly between coats.
Allow the surface to dry for at least two days before placing furniture or walking on it.