Exterior: Glass
First make sure that you clean the glass surface with a soap intended for automotive use.
What you'll need.
Once your glass surface is clean and dry apply a non-streak glass cleaner with a micro fiber cloth. It cleans very well and of course dries without leaving streaks. This product is stronger than soap yet it is said to be safe on window tints. As always be careful the first time you use it. Try it in a less noticeable spot first. Clean from top to bottom. Apply until the surface is nice and dry.
You may also want to coat the surface of the glass with a water repelling product. Instead of the water adhering to the surface such a product will bead the water that comes into contact with your windshield and promote its rapid dissipation. The faster the water is out of your line of sight the better you will see the road. As an added bonus these products make it easier to remove ice and snow buildups on the surface in the winter. In Montreal we see a lot of precipitation in the fall and winter it is a wise investment to make sure we have good visibility.For interior glass you may use the same procedure. Also what I find helps a lot is an anti-fog formula. Apply it to the inside windshield and mirror. In the winter when its really cold outside condensation will develop on the glass surface. This will reduce visibility.