The budget for our family of 5 is $350 a month. Most months I am at or below that. It includes all paper products, but not eating out (a couple of times a month) or any little candy treats my DH has to have.
I clip coupons and shop between 4 stores, all close since I live in a metro area. If one of those stores has good coupon specials, I'll group my milk purchases to help get the $20 required for that coupon (ex. 1 lb. bag pre cut baby carrots for 8 cents). I plan a menu for the week, take a list (and not my husband) and stick to it. If one of my "staples" is a good price, I'll stock up. In a recipe that calls for 1 lb of meat, I'll try to cut it down. My cooking is simple, since I'm not very talented, but it's meals my family enjoys.
When I was working FT, we ate out and grabbed fast and convenience foods frequently. That adds up to a lot of money. Keeping the grocery bill down requires some time--and I enjoy it, it's almost like a puzzle with rewarding results.