Buy paint or stain to match your existing deck. If you can't find an exact match, consider painting over the entire deck with a darker shade.
Spread drop cloths around the edges of your deck to catch debris and paint. If possible, slide the edges of the drop cloths a foot or more under the edge of the deck.
Put on a sunhat and apply sunblock to all exposed skin. You can burn surprisingly quickly on even an overcast day.
Vigorously sweep the deck to remove dirt, cobwebs and other debris. Follow up by washing the deck with a spray from your garden hose. Allow to dry completely before continuing.
Scrape off loose paint using your paint scraper. Don't dig into the wood. Instead, apply long, even strokes to remove just the paint that's already peeling.
Sand down edges where remaining paint meets exposed wood. At each point, sand until you can't feel a bump with the ridge of your thumb. This smooth transition will help the appearance and durability of your final paint job.
Apply a coat of paint to the exposed lumber. Use long, even strokes at each point and feather out the paint as it crosses over onto painted sections of the deck. Allow the paint to dry.
Apply a second coat of paint over the entire deck. Use long, even strokes and paint in the direction of the line of your deck beams.