Wash with a good car wash, rinse, dry.robg said:
I wash only in the shade, and I shampoo/rinse/dry panel by panel. Slow but great results. Then I use a quick detailer spray to finish it up. No water spot problems.
For the hardcore folks, use distilled water to rinse. I did that today. Even if it dries on you, it shouldn't leave water stains.