Shut and lock the windows, and when you’re working, avoid spraying windows directly. With this kind of power, water could seep through the sides and into the house. You’ll get wet, so dress to enjoy it.
Set yourself up with the least powerful nozzle, numbered 40 or thereabouts (which indicates a fan-spray pattern of 40 degrees, if you must know). Stand at least three feet away from the house and spray a small area. Stop and check to make sure the spray is not damaging the surface.
If you’re using only water, work from top to bottom in segments. (No need for a tippy ladder; you’ll be able to reach from the ground.) You may choose to switch to a sharper (lower-numbered) nozzle to dig into cruddy corners, but in many cases, the #40 nozzle will get the whole job done. Keep the spray moving, and always do the entire house. Spot-cleaning just parts of it could leave the place patchy. If you’re using a cleanser, wash from the bottom up, then rinse with fresh water from the top down.