A bowl of warm water, a quirt of kitchen dish soap, a clean towel and some elbow grease. Wring-out the towel frequently and wipe with an over-lapping pattern. After that, follow-up with household window cleaner (windex etc) and a micro-fiber towel. My windows were slightly hazed from 3 months of winter. In less than 15 minutes, the windows were cleaned as described just yesterday. On the way to work this morning, I felt like I was driving Mr. Clean's car.
Ray