There are lots of window cleaning products to choose from, ranging from industrial to organic. Try this old-fashioned classic recipe from Living Well, Spending Less. Mix 1-1/2 cups white distilled vinegar with 1-1/2 cups water, with 5-10 optional drops essential oil (we like geranium and sweet orange). Mix in a spray bottle, spray on glass and remove with a clean dry squeegee. Polish with old newspaper for a streak-free shine.  Also works on chrome and countertops.