Well, there are only two of us. My bf works at a hospital and sometimes buys his lunch there, or he takes leftovers. We eat out (fast food - cheap and I normally don't pay) about once a week, but that's not factored into groceries.
I visit about 4 coupons sites and use coupons with sales. Arm and Hammer toothpaste was on sale for 1.99 and I had 2 $1 coupons, so I got two things of toothpaste for 99cents. I buy lean ground beef and freeze it into one pound packages as soon as I get home. We drink organic milk. Since there's only two of us when we cook, we always have leftovers. I also only buy what I need to make meals. I'll make a list of meals that we routinely eat (wet burritos, chicken dishes, rigatoni) and only buy ingredients for that. We don't really buy prepackaged stuff - I do buy pudding cups because I love them lol. But I only buy them when they're on sale, and then I stock up. We do things like buy a big thing of applesauce for a little over a dollar, and put it into individual containers for the refrigerator. I typically take a thing of applesauce and a yogurt for my lunch at work (I work third shift 2 days a week).
In an effort to get bf away from drinking pop, we get gatorade, but if you buy the powder you get basically two large containers for the price of one. We typically buy cereal in the bags - so much cheaper it's crazy. We stock up on bread when it's on sale and freeze it. When I shop, I evaluate if I really need it or not. Right now, we are out of sandwich bread (I buy the cheap white bread for french toast, and we have that) and also out of PAM spray. However, it seems silly to go grocery shopping for just that, so I will make bread in the bread machine and use butter and flour when I bake until there's more that I actually need.
Basically I only buy what's on sale or with coupons when I go, or if I can't find it on sale, I'll get the store brand (depending on what it is). And I stick to my list and my list of ingredients for meals.
Hope that helps!