Getting rid of stubborn smears on glass - Roger Jones
Just a little practical tip, not unknown, I'm sure:

I had a persistent smear the length of the wiper blade on the windscreen of my Golf, where the left-hand blade finished its rightward travel, which became very annoying and even survived the valet's repeated deep glass cleaning. I've got rid of it simply by loading an old toothbrush with toothpaste and scrubbing the line thoroughly.
Getting rid of stubborn smears on glass - Armitage Shanks{P}
Toothpaste has been mentioned before. I also recall somebody mentioning vinegar wiped on with crumpled newspaper; some combination of the ink and the vinegar I think.
Getting rid of stubborn smears on glass - PoloGirl
My nan swears by polishing the glass with newspaper, and she knows *everything*!

Getting rid of stubborn smears on glass - THe Growler
Newspaper does work, also rubbing alcohol to clean the grime off the blades and the screen.

My old man used to use silver paper from his fag packet to clean up chrome as well..........