You know that bucket of glass-cleaning supplies you carry through the house when it's window day?
There should not be a roll of paper towels in it.
Paper towels leave not only streaks, but linty ones. Instead, go for a microfiber cloth, a squeegee, or, best yet, a handful of newspaper. Your morning read does an amazing job on glass.
If you go with the newspaper, be sure to wear gloves. That ink gets everywhere.
Finally, the finishing touch.