I love to use coupons and get them out of the Sunday paper every week. For me it's a fun hobby, I have them organized in little sections in a card box - shampoos, toothpastes, laundty soap, cereals, soaps, cosmetics, general food, general non-food and then within those caregories, by date. I shop at chain grocery stores twice a month (otherwise I'm at Trader Joes or Whole Foods) and always go through my coupons before I go to the store, then I just write down on my shopping list whatever items I'm going to use the coupon for. I usually save between $30 and $60 on maybe a $150 shopping bill.
This works well for me because I'm not fussy about most brands - I will use whatever toothpaste, toilet paper, canned tomatoes, or whatever, I have a coupon for. Sometimes I have a coupon for an item I might otherwise not try and I do sometimes try new things that way. If I really preferred certain brands of things, this would not work as well.
Also, as another poster said, I have read that buying generic brands, and comparing prices really carefully, will save you more than using coupons. I think that is probably true but I'm not willing to comparison-shop that way. So I figure I am saving some money by using coupons. It's pretty exciting to see how much you've saved every week!