My family ran a fast food (as in just about everything deep fried) restaurant when I was a kid. Every weekend my job was to wash the big windows all around the restaurant. This is an inexpensive, easy and best of all, environmentally friendly recipe for shining windows:
Add 1/2 cup ammonia or white vinegar to one gallon of water. Wash windows with a sponge or white cotton cloth then wipe dry with crumpled newspaper (the daily newspaper, not newsprint) and your windows will be sparkling clean and streak free.