Power Wash or Sweep
Getting started, remove the Grill, furniture and etc off the deck. Then power wash or sweep it to remove leaves and dirt. Use something thin like a putty knife to remove any debris stuck down in the spaces between the boards.
Using a Cleaner
Now use a standard deck cleaner to remove stains. Make sure to follow the directions as some cleaners require the deck to be wet before applying. Use a stiff-bristled brush broom to apply the cleaner. Once the entire deck is cleaned, let it soak for a period of time. Make sure you follow the directions of the cleaner.
Drying Time
Once it has set for recommended time rinse thoroughly. Allow the deck to dry for at lease 48 hours.
Sealing
Before starting make sure you use proper safety. Wear Eye Protection, Safety Mask and a pair of Rubbers Gloves to applying sealer.
Now its time to apply the sealer. Use a Sponge or Roller to apply two thin coats. Use a brush for railings. Allow the sealer to dry completely (48 hours) before moving anything back onto the deck.