Either the obvious - cover it with paper / rug etc., or wash it down with warm (not hot!) water last thing at night, and then spray it with de-icer. Should do the trick.
4th solution - sell the car, buy a bike (healthier and more environmentally friendly)
ok not the solution you were after. Either cover it or park it in a garage. A "not very ideal but effective" way would be to sprinkle salt over the screen the night before
Do not pour salt anywhere near your car unless you want to wake up and find your car rusting well ahead of it years! There is enough of the stuff splattered over the roads in cold weather without pouring it over the body work when you get home.
As suggested cover the windscreen at night. You can by 'covers' specially for this purpose from petrol stations, Halfords or even just use sheets of newspaper pinned down to the windscreen with the wipers.
leave the engine running with the heater on! At least it will be nice and toasty for you in the morning unless you live in a place like me where some bxxxxxxx will have nicked it and burnt it out after removing all your tools !!!