[CajunBMW]

Great advice above. I can only note how I maintain my car. In north Louisiana we have hard water with lots of calcium, which as noted by others above stinks if you let the water sit on the car. I recently had my car (glacial metallic silver) ceramic coated and that has made everything much easier. I didn't really change much from what I did before, but the ceramic coating definitely has made things easier and looks better. For a quick wash, I use the optimum no rinse as @billfitz noted and then towel dry. If I have more time, I use the Meguire's hybrid spray and then rinse off and towel dry. Usually looks great. Certainly the key for me is not to let the water sit on the car as i definitely get water spots quickly.