It has taken me years to get the hang of couponing and not waste money buying junk I didn't need. 
The way to save the most with your coupons is to use the coupon along with a sale price on the item.  I NEVER use a coupon on a regular priced item unless it is something I HAVE to have and it usually never goes on sale.  Get your sale ads or go on line to a site that will tell you all the matching ads that go with your coupons.  Another way to make the most is to keep your eyes open for any circulars or booklets at the entrance to your store, or sometimes on the store shelves.  If the coupon says STORE COUPON, then it can be coupled with the manufacturers coupon for that product for extra savings.