Robg, these are my rules to washing(which also avoid water spots)
Never wash in sunlight, find a shaded area.
Use a two-bucket method, 2nd bucket is to rinse the wash mitt.
Don't use TOO much car shampoo, and use hot water to fill the bucket to about 2/3 mark, then swirl the water by hand to make sure the shampoo has time to break up, then give it a shot of cold water from the hose to "Foam" the water up, you should end up with a nice "head" of foam.
Do the finish first, the bumpers and wheels last, try to use a different wash mitt for the finish and the bumpers/wheels (I use 3 as mentioned in another thread)
Turn the wash mitt over after each wipe.
Use linear motions when washing, not circular.
Rinse with a straight hose, let the water "sheet" off the finish, rather than spraying it when rinsing.
Wipe dry ASAP, I actually wipe it dry before beginning on my wheels. I like the CWB and Syn. Chamois.
Use a good detail spray and cotton towels to 'finish', should only take ya about 10 min. and the detail spray I use takes out any water spots.
Water spots are more apparent on finishes that are not or have not been waxed in a while.