This first part is one that some will doubt but it is cheap and does work wonders

Use "Pledge" Furniture polish on the plastic windows. Re apply regularly.
Washing the vinyl with just liquid soap Lux or other soft soap in water will do great
If you go though a car wash make sure they DON'T spray their wax on it.

I am hoping others will put what they are using to keep it looks good

 

It's a jeep, a good coating of mud looks better.

 

Huh, Pledge eh...I had no idea....will give that a try when my Best Top Window Cleaner runs out.
Thanks!

 

Spray it on and wipe from side to side with a soft cloth NOT in a circular motion