Windshield
Clean the inside top to bottom (vertical movement) and exterior horizontal. That way if you see streaks you'll know which side of the glass it's on.
Cleaning the Inside of the Windshields
Use an alcohol based cleaner so no streaks are left on the windshield. After cleaning, buff the windshield with a dry microfiber towel to get rid of any excess residue.
They make triangle microfiber clothes on a stick that make it easy to reach into the corners.