I know this is an old thread, but I've had amazing results with using RainX. It helps prevent snow, freezing rain, and ice from accumulating. Even when it does build up, it makes it Much easier to scrape off. RainX brand also makes defroster sprays that work well to help break up accumulated ice as you scrape. It has RainX in the deicer, so it also helps to maintain the RainX on your windshield. This trick works so well that I use it on all of my car's outward facing glass, including side mirrors.
As mentioned in other answers, using the car's defroster setting is a good add to the procedure.
Using all of these options gets the ice started to be removed from the glass from both sides of the ice. This greatly improves your ability to scrape it off with an ice scraper.
I first added RainX to the ice scraping routine almost 2 decades ago. The ice that winter was as thick and hard as I remember ever seeing. I broke countless scrapers, to the point where I would buy 2-3 ice scrapers every time I saw them available. We're talking +3/4" ice every morning and every night for at least a week, and that was under +6" of snow drifts on the car. Sometime during that week, I applied RainX to my windshield, side windows, and rear window. The next time I had to scrape, the ice came off in large chunks, instead of finely shaved ice. I didn't even break the scraper!
When I found the RainX brand deicer years later, I got some and have now been using it for many years. It works great on frost as well as thick sheets of ice. I even use it in the summer to put down a quick layer of RainX. For $4 a can/bottle, I feel it's well worth freezing my fingers less and getting to work sooner. I used to give it as Christmas presents!
As an added bonus, RainX works while you're driving. It lets your wipers remove splashed slush, falling snow, etc. better. If you turn up your front defroster, the snow that turns to water slides off really easily. RainX brand also makes a wiper fluid that has RainX in it, which just so happens to be rated down to negative thirty-something degrees Fahrenheit, which helps keeps your windshield coated with RainX and free from freezing sh-tuff.
Full disclosure: I'm not in anyway endorsed or paid by RainX, I just really love what it does for me.