To wash commercial, or storefront windows, you need a couple of tablespoons of dawn dish soap mixed with a few gallons of cold water.

You can use Ettore or Sorbo squeegees, I recommend a wide assortment, like a 6",10", 18", and 24". Pretty much any applicator will do, but I prefer Unger. You'll want a 10",18", and a 24" applicator.

Also, you'll need a telescopic pole, I recommend a 3 piece 12ft one. These, with lots of clean dry rags, and you'll be good to go.

If you have something on a window that your regular solution won't take off, I recommend using a few tablespoons of ammonia with your regular cleaning solution. The smell is awful, but it works great for outside windows, or construction clean-ups, where the customer will not be bothered by the odor.