As a general rule, I don't use coupons. For one thing, we do not get the paper delivered, and therefore have limited access to Sunday coupons. There was a time, long ago, when I conscientiously clipped coupons and tried to use as many as possible when I went grocery shopping. After a while, I realized that I was often making purchases for the sole reason of using that coupon, and buying items I did not need or use. The end result being that the "almost free" items sat, and sat, and sat in the pantry until they were past the expiration date, and then I had to throw them out. You often hear about "Coupon Queens" who purchase cartloads of grocery for minimal outlays, but it makes me wonder if they really need all that "stuff"?
Another reason I don't use coupons is because I rarely use or need items that manufacturers print the coupons for. I don't buy frozen dinners or convenience foods at all. I use canned vegetables and fruits, and keep a supply of canned chili, but that's about it. Have you noticed that you never see coupons for staples like dried beans, rice, dried pasta or fresh vegetables? You save money by buying unprocessed items.
I once waited in line at our local Walmart behind a family of three: Mom, Dad and a boy who was about 8 or 9. Everything they had in their cart were in boxes. Boxes and boxes of frozen dinners, pizza and hot pockets. cookies, crackers, and bread. I think the only fresh thing they had were some bananas. I really felt sorry for that boy who, I suspect, hardly ever ate a true home cooked meal. But more importantly, think of how much money was being wasted by his parents who don't want to spend a little time preparing nutritious meals? They were literally throwing money away! Even if they were using coupons, they were not saving any money!
I think the better approach is to buy things you actually use when they go on sale as loss leaders at the grocery store, and try to stock up so you have enough of that item until it goes on sale again. I have been using this method for staples in my pantry. As long as you have the room, this is the surest way to get the lowest price.