One of the best ways to maximize your savings is to use a coupon on an item that is also on sale. In fact, to get the most benefit, when a particular item is on sale, you should buy enough of that item with your coupons so that you never buy it at regular store price. This buying philosophy is commonly called "stockpiling" in the coupon world and is a great way to ensure you are getting the best deals.
For example, if Colgate toothpaste is on sale this week at the grocery store for $1.00 (locally, it was recently), then I pull out my Colgate coupons of $.75 and I buy as many tubes as I have coupons for free after my coupons are doubled to $1 off. Now, you need to be careful here. Some stores will only allow you so many coupons for the same item per transaction. Yes, I have gone through the checkout line, put my items in the car, and come back in the store for another transaction! Some have even divided up transactions on the conveyor belt and ask the cashier to ring them up separately. But, I have found that this will slow the line down, making the people behind you not too happy, and can even upset store management. I always try to be very conscientious and sensitive to other people in this area, so for me, a trip out to the car is no big deal if it makes everyone happy.
Another note of caution here, make sure you know your favorite store's coupon policy. They vary a lot even within the same chain. For example, I have found that one Meijer's store will double up to six coupons for the same item; but, another Meijer's policy is only two. That can make a big difference in your savings.
One last note of caution, some stores will frown if you walk in with, say, 20 Colgate coupons and wipe them out of toothpaste. Be considerate of others here. Perhaps a good idea here would be to buy 10 at the beginning of the week and 10 at the end after they get another truck in to restock. That way other shoppers can take advantage of the sale, and you don't wipe out their inventory in one trip.
That brings me to my last point here. Don't hesitate to get a rain check for an out of stock item. Some people don't like to get them, but for me, a rain check allows me to buy the item on sale, when I want and when I have the most coupons for that product. The timing is in my hands and I can use it to my advantage.
This buying philosophy helps you to stock-up on the items that you need without having to pay full price. I realize that some may not be able to do this for lack of space. For me, I keep items on shelves in our basement. When someone needs something in my family, they jokingly say, "I'm going to Mom's store", for whatever it is they need. And in most cases they will find it.
So, in conclusion, use coupons in conjunction with sale items and you will find you can save a lot of money off your total bill for groceries, health & beauty items and toiletries. For information on how to accumulate coupons, see my article "where to get coupons".