There are all sorts of options out there..... but I use toothpaste
Yes folks.... toothpaste
. It's a mild abrasive and just the perfect thing for getting grime and crap off the glass. Method....
1. Wash the windscreen off with water only
and allow to dry.
2. Use a microfibre cloth (any cloth will do, but I use microfibre) to 'brush' the screen with toothpaste.
3. Allow the toothpaste to 'haze' (start to dry off) then brush 'some' more. Work in a circular motion and really 'work' the toothpaste into the screen.
4. Rinse off thoroughly and dry the screen - make sure you clean any residue off plastics too.
5. Apply a treatment to the screen if you wish, I use Rain-X.
6. Kick back, have a beer and admire your super-clean windscreen and the nice minty smell coming from your hands
Incidentally, 'smokers' type toothpastes or powders are the best for the job.