I wash my all of own windows and I am a fanatic about them looking bright and clean - with no spots. I use Windex and paper towels and clean them thoroughly when the sun is not shining on them.

I use to clean them in this fashion every time it rained but, by accident, I found out that I can simply hose all of my windows down after a rain storm to keep them looking clean. Now I hose them once a month or so and I even started doing this with my car as well. What a time saver and what a difference it makes!