Clearly, the correct way to defrost or de-ice your car is to pack your spouse or significant other into some wellies and a warm coat, hand them a scraper and let them get to work while you go back to bed with a cup of hot chocolate and a laptop to read CompleteCar.ie...
Assuming that's not an option, there are a few pointers you would do well to remember...
Definitely de-ice your car
Sounds stupid, doesn't it, but the worrying fact is you will see people driving around peering vainly through an opaque sheet of frozen water on their screens. Or, they'll have cleared the widscreen but not the side glass or the mirrors. Visibility is key when driving, so make sure you allow time in the morning to clear all your car's glass before setting off.
Leave it running? Risky...
One of the simplest and lowest-effort ways to clear everything up is simply to start the car, turn on the heat full blast, switch on the rear-window de-mister and then head back into the warmth of the house until everything's ready. It's an elegant solution and has the added bonus of your car being nice and warm inside when you do get going. But it's risky – the AA has warned of car thieves loving this time of year because de-frosting cars, left unattended, are easy prey. There's also the issue of you wasting fuel and harming the environment by leaving your engine running unnecessarily.
The great water debate
Many of us will abandon the scraping and scratching routine and simply head out with a kettle of hot water to blast the ice off the screen. Beware of this method though - glass becomes more brittle when it's cold and a sudden change of temperature can cause cracks, or if the glass is already slightly chipped or cracked, then it can cause dramatic shatters. If you are going to stick to the water method, make sure that the water is actually only tepid or lukewarm at most. It's also a good idea to add a little alcohol (white spirt is best, or hey why not some Vodka?) to aid the ice clearance. Using water to clear the screen also means you have to do it right before you go, as you'll have to use the wipers to clear and excess before that starts to freeze too.
Use some chemicals
Now, perhaps in an environmental sense we shouldn't be dumping too many chemicals into the system, but a quick spray with de-icer can clear a screen in seconds, so perhaps it's worth the risk. Of course, most of us won't think of buying de-icer until it's already icy, but if that's the case don't fret - screen wash usually contains some anti-freeze element to stop it freezing up and clogging your windscreen washers, so a splash of that on the screen can be just as good. Again, remember to wipe away anything that's left before that starts to freeze too.
Use high quality tools
If you're going to get out there and start scraping, make sure you're using a decent scraper - don't rely on the 20-year-old one you just found in the back of the garage, as the rubber will have aged and split and you could pretty quickly find yourself scraping some big scratches into your glass. Don't try and use the wipers as a scraper substitute - wiper rubber is soft and easily damaged, so it's no good for this task. Equally, don't use your wipers in auto mode if it's frosty, as they can scrape and tear themselves on icy patches on the glass, and it can be bad for the wiper motor too. Finally, don't forget to get a good quality soft brush for clearing snow off the roof and other panels - again, it's something you need to do to maximise visibility and also not to be dropping drifts of snow on other road users, and the soft brush will make sure you won't scratch your paintwork.