Streaks on your windows are usually a result of too much cleaning solution left behind when you clean your windows. The best way to combat this is by finding the right cleaning solution and material to properly wipe your windows.
Generally, a soft, lint-free microfiber cloth is the best material to wipe your windows with. It will not leave streaks behind the way that paper towels or even ordinary towels will. In combination with any of the following cleaning solutions, you should never have to deal with streaks again.
The three solutions listed above will all work in combination with water to provide you with streak-free windows. Mix them in a spray bottle and apply an even misting to your windows each time you go to clean them. Wipe from top to bottom and then left to right. If any stains or spots remain, try again with a dry microfiber cloth.