If you haven't organized your shopping list with coupons before you've gone to the store, don't give up. Keep your eyes open for coupons in the store.
Blinkies: Look for red SmartSource coupon boxes attached to shelves with manufacturers coupons, referred to as "Blinkies" in the coupon world. If you don't need the item right away, take one for your coupon organizer and hold onto it until the item is on sale, or until it's on sale at another store.
Tearpad coupons: Many product displays will have a tearpad of coupons attached to it.
On-pack coupons: Many products have coupons attached to the item. If you buy the item, be sure to take the coupon off and hand it to the cashier. Do not expect that the cashier will take the coupon off because it can be missed easily as they scan items quickly.