First impressions are important, and if you’re religious about manicuring your lawn, you’ll want your home’s pristine exterior to complete the picture. Plus, an exterior "freshening" a couple of times a year allows you to spot and repair any problems before they become major issues.
As with all cleaning, it's best to dissolve soil rather than aggressively scrub it off. Pre-spray areas to be cleaned with water and a detergent solution (use a garden hose fitted with a detergent dispenser). After a few minutes, gently scrub using a long handled brush, rinse and inspect your work.
As an option, why not buy or rent a pressure washer? You’ll need a garden hose that attaches to this pump machine, and water will spray at 1500 or more pounds per square inch (or PSI): handle with care and practice first, following the manufacturer's directions. Off comes dirt and dust, bird droppings, tree sap and more. Plan your wash top to bottom, to keep dirty water below what’s already cleaned. You’re not removing paint here, so don’t hold your washer nozzle any closer than two feet and not just in one spot.
Look around for other maintenance issues. Are shutters loose? How about roof shingles? If so, head for the attic and observe whether moisture is seeping through the roof, which should also be evaluated at the joints. Is exterior paint worn or chipped? Bricks loose or outlets in need of safety repairs? Get gutters before they get you. Leaves and sticks clog gutters, which then trap rain that freezes when temperatures drop and can cause damage. This might be a perfect time to install gutter covers. Read more on home maintenance.