We've just re-assessed our grocery spending. By doing the following, we've managed to cut our spend down by 1/3 to 1/2. We had gotten quite stupid with our grocery spending, so if you're already careful then you probably don't have nearly as much fat to cut from the spend as we did. Exact amounts will be meaningless because of the different country thing, and the family size difference, but I found that the biggest 3 changes were:
1. Menu plan. It really does work. I look in my cupboards and plan to use what I already have first, then add any needed item to the shopping list. If it isn't on the list, it doesn't get bought. If I leave off anything major then it gets added to next week's list. Over time, my list making is getting better. Leave yourself some wriggle room to make the most of seasonal specials. If planning on a stir-fry, for instance, I'd write "carrots, bell peppers if cheap, something green and leafy (cabbage/spinach/broccoli etc), something for crunch - green beans?". That way you're not locking yourself into buying expensive spinach if cauliflower is half the price.
2. Chocolate (or whatever your weak point is - wine? excellent coffee?) is a luxury item. I put myself back in time and pretend that this one purchase needs to do me for 3 months until the next boat comes in. Either eat it all in one hit or spread it out in tiny morsels, but either way, once it is gone, it is gone. And don't bulk buy just to get around it :) We buy 85% cocoa organic dark chocolate, and in our stupid days were eating more than 2 big blocks per week. Now that 2 blocks is 3 months supply. It is a treasure to be hoarded and gloated over for special occasions.
3. Food shopping is a once per week activity. Full stop. No excuses. If I run out of coffee then (after having a minor tantrum), I drink tea or cocoa until the end of the week. If we run out of potatoes, we eat rice. If we run out of onions and garlic, we have less interesting food for a couple of days. And next week's shopping list is better.
Oh, and in general I plan one soup (bone plus leftovers) and one meatless meal per week (we're semi-paleo. I know, I look back on my semi-vegetarian college student self and can hear her scoffing from here, but there you go. Life is a funny thing.) Planning it means I remember to soak (and sprout) the chickpeas ahead of time, etc. The semi-paleo thing also means we just don't ever buy things that are pre-mixed or highly processed. If we want snacks it is fruit, nuts, popcorn (not the microwave stuff), or we bake it ourselves.
The longer I menu-plan the better I'm getting. I can now plan a roast chicken for Monday, make chicken stock in the slow-cooker overnight and have chicken soup on Tuesday. Or cook a double lot of spaghetti sauce one week (eaten on sweet potatoes), and plan to use it again the following week with potato wedges or steamed veges.
If you want grass-fed meat, look into buying it by the half-beast. May or may not be cheaper, depending on where you are etc but definitely worth exploring if you have room for a big freezer.