Over time and with many miles, the windshield on any car will become dirty and blurry; using these techniques can solve all those problems.
The first thing to do is to get Rain-x, invisible glass, and some old rags. Rain-x seems like best product for outside windshield to remove all the dirt and grime that has gathered up.
Using the invisible glass will ensure that the inside glass is clear and pristine. The towels will ensure that the glass stays clear and leaves no marks from use. Watch this video for more: