Some pressure washers come with an assortment of color coded spray tips. Each one has a different spray from the high pressure pin point spray to a wider low pressure spray. A tip that produces a spray about the width of a 2x4, with medium pressure, is perfect for washing decks.

Assemble the pressure washer by attaching a hose to the intake valve and the "wand" to the appropriate nozzle.

Make sure the safety latch on the wand is in place and then start the motor. It starts just like a lawn mower, but keep in mind that once the motor has started, pressure starts building up right away, so don't let the motor idle for long. The jet from a pressure washer can be 50 times more powerful than a garden hose. So it can do a lot of damage if used incorrectly.

Release the safety lock and point the wand away before pulling the trigger. Never point the wand at another person.

With a steady "sweeping" motion, move the spray back and forth across the deck surface. The trick is to keep the spray moving. Don't rest in one spot for too long or it could permanently damage the surface. Steadily move the jet back and forth across the entire deck. The difference after each pass will be noticeable. A cleaning solution can be added to help with those tough spots on the deck.
Let the deck dry and then apply a sealer to protect it from the elements.

Use the pressure washer to clean other surfaces around the house. Use it on brick walls to make sure every nook and cranny gets clean. Siding can be cleaned with a lower pressure spray tip. It is also useful for removing algae stains from a backyard fence.