Where do I go wrong at the grocery store???

Lately I have been reading a lot (and I do mean a lot) of blogs where people are only spending $40-$50 a week on groceries for a family of four. I spend at least $100-$125 a week on groceries to feed my family of four. Where do I go wrong? I don't clip coupons. I don't know how. Is there some secret to it? Do I need to take a class on how to clip coupons and save money on my groceries?! I don't mind spending the time to organize and do it but I don't even know where to get started. I have seen the websites that you have to pay and they will help you in the coupon arena. I guess they tell you what is on sale where and what not? I don't want to/need to spend money on that. I just need to learn how to do it on my own. We have got to get on a budget and now. Ugh. One more thing that I need to learn and do...