Check out a website called smartcanucks.ca. Great site for saving money.
You *can* stack coupons at some places, London Drugs & Superstore, for instance, but not to the extent that they can do in the states. And, it depends who is working at the till. Some will allow it, some won't. But, even with stacking, some of these places aren't always the best deals. You need to read the coupons carefully to. If it says only one coupon per transaction, then you can only use one per transaction. You also cannot use a coupon to stack that has the same barcode.
I don't think it will ever be possible to get grocery prices like they do in the states. They also have royalty programs that are far superior than our programs (think Co-op, Costco, Save on Food, Sobeys). Even with those programs, I could never get $200+ off of my groceries at a time. I don't shop enough at those stores to get that sort of deal.
If you watch your flyers carefully, you can price match. I know people who do this, but personally have never done it myself. I used to spend $700 + on groceries a month, but have now gone to about $450 just by watching sales and going on the coupon sites mentioned by Carina.
Also, think about what they save money on. How often do you see coupons for fresh fruit and vegetables? How about lean means? When you watch that show, look at what they are buying. Lots of juices, sugary foods, processed foods, etc. I want to feed my family with healthy, wholesome foods, so I spend the money to do that. I look for whatever fruits and vegetables are on sale for the week, and I buy those. I watch for sales on meats as well. We freeze meat (no more than 3 months), so we stock up on the deals when we can.
