Stacking coupons is when you have a mfg coupon and a store coupon. When you go to the store and have both of these coupons, always give the cashier all of your mfg coupon first, then the store coupons. For example if you have a mfg coupon for peanut butter (not using brand names) for 75 cents and a store coupon for the same brand of peanut butter for 50 cents it will deduct $1.25 from your purchase. I try to match up my store coupons with my mfg coupons to maximize my savings. Another good tip is to make sure you get credit for all of your coupons, there is no way I have time to add them all up before I get to the check out, but I make sure I have all my items on the counter and even if it means the cashier has to wait a minute, I watch as each one of my coupons is scanned. Another way is to hand the coupons over to the cashier one at a time. Just don't get distracted and let them miss one or two of them, it's easy to get distracted, that's why I was thankful when my granddaughter went back to school, now my full attention is on my purchases.
Hope this helps.