Check into couponing sites that specialize in your area. You'll find some stores are more "coupon-friendly" than others, meaning their coupon policies may allow you to double-up, etc.
For example, say there is a $.50 manufacturer coupon for a bag of beans, and a $1.00 store coupon for the same brand of beans. A coupon friendly store will let you use both, so you'd save $1.50 on that bag of beans. Of course, if you get 10 bags of beans, you now just saved $10.50. (assuming they allow you to use multiples, etc.). So, that's what I mean by coupon-friendly store. For an average couponer, expect to spend about an hour to two before a big grocery trip. More extreme couponers spend hours readying for the trip, but of course, save much more.
We typically shave about 45%-65% on average off our bill with coupons....depending on the deals and coupons. So not doing them is like throwing money out the window.