When it comes to saving serious money on your grocery bill, seeing is believing.

It's why Faye Prosser of Cary, N.C., keeps a collection of old grocery store receipts in her kitchen, reported WYFF-TV in Greenville, S.C.

"At this particular store, they were tripling coupons and my subtotal was $63.84," Prosser said holding up a receipt. "And they paid me $8.29 to take (the groceries) home!"

Prosser had a receipt for $531 worth of groceries purchased for $47. She had another receipt for $55.28 worth of groceries that cost $1.87 after coupons. In fact, the stay-at-home mom said she never spends more than $50 per week on groceries.

"We were spending anywhere from $135 to $150 a week, and it was just my husband and I and an infant," said Prosser. "Now we're at the point where our grocery budget is to $50 a week, which is about a savings of $4,000 a year from what we were spending."

Prosser's secret to cutting grocery bills is knowing how and when to use coupons. Her book, The Smart Spending Guide, explains the process step-by-step.

"I tell everybody, it's not rocket science. Anybody can do this. I'm not some crazy coupon genius here. There are lots of moms out there just like me that are doing the same thing," said Prosser.

Prosser's pantry is packed with food items she bought for little or nothing with coupons. There are rows of rice, beans, salad dressings, croutons, pancake mix, aluminum foil and sandwich bags. It's what Prosser calls her "overstock."

"When I run out of something in my cupboard, all I have to do is walk around to my overstock and grab the next one out that I paid a fraction of the cost of retail for," said Prosser. "Maybe it's that $2 bottle of shampoo, and all of a sudden I run out, so instead of running to the store to spend two more dollars, I purchased five when I had a coupon and they were only 25 cents."

The television station accompanied Prosser on shopping trip to a grocery store near her home. Within minutes, Prosser scored her first deal of the day. Lipton Tea -- her husband's favorite -- was on sale for 99 cents a box.

"The coupon is for 50 cents off any Lipton Tea product, and this particular box is 99 cents," she said. "At this store, the coupon will be doubled, so the product will be free." Because Prosser had more than one coupon, she gets several free boxes to store in her pantry.

Then it was off to the cereal aisle for another coupon freebie. On this day, Life cereal was on sale for $1.99 a box. Prosser has just the coupon for that.

"I have two $1-off coupons that I found on eBay," she said with a smile, "Free, free, free, free."

Prosser's shopping cart quickly filled with free bottles of White Rain shampoo, a free box of ZipLoc sandwich bags and several bottles of Dial Liquid Hand Soap, purchased for 64 cents each.

Finally, it was time to check out.

Prosser paid close attention to the cashier to make sure each item is scanned correctly. The subtotal for the basketful of groceries was $91.59.

Now it was time to subtract the coupons. Again, Prosser kept a close watch on the process, to make sure her coupons were doubled, and other store discounts were added. Her final bill? $13.67 -- a savings of more than 85 percent.

"It's an amazing feeling," said Prosser. "Rowdy. Very rowdy indeed, and full, because we're going to have a great pantry."

This was not a one-time thing, reported the station.

Prosser said she saves 80 percent or more on groceries every time she shops. She said you can, too, by following a few simple steps:

Step One: Acquire Coupons

To use coupons, you must have coupons. One place to get them, of course, is from the Sunday newspaper. Each newspaper contains three to four coupon inserts. Prosser recommends you buy more than one copy of the newspaper, or ask your friends and neighbors for their coupons if they don't use them.

Another source for coupons that Prosser recommends is TheCouponClippers.com. There, you can choose which coupons you want.

The coupons are free -- it's illegal to sell coupons -- but there is a "handling fee" for each order. Prosser said for every $5 she spends, she saves $80 to $90 at the store after the coupons have been doubled. Remember: you'll need multiple coupons per item to buy several when it goes on sale.

Step two: Develop A Price Book

A "price book" is simply a list of items your family uses at the best price you can find them for at the grocery store. For example, if your favorite brand of cereal costs $1.99 on sale, write that down, and include the name of the grocery store that sold it for that price. Price book totals are the very best sale price, not the price after coupons. Prosser said your Price Book should include:

The name of the store where you found the good deal, the name of the item -- specific brand, the category it falls under -- dairy, canned goods, etc., how much you paid, the size or weight of the item to determine the price per unit.

The "price per unit" helps you compare big boxes to little boxes. It allows you to determine if a $2-off coupon on a large item is better or worse than a doubled 50-cent coupon on a smaller item. The price per unit is derived by taking the cost of the item, divided by the number of units.

For a $1.99 box of cereal that is 18 ounces, you would take $1.99 divided by 18 ounces, and that gives you the unit cost, which is 11 cents.

Step Three -- Prepare Your Grocery List And Meal Menu

Once your coupons are clipped and organized, and your price book is well under way, it's time to prepare the grocery list. For this, you'll need the weekly sales fliers, which come out each Sunday and Wednesday.

Prosser said if you go into a store without knowing what's on sale, you're going to spend more money. She makes her grocery list according to what's on sale, and according to her meal menu. Prosser prepares a seven-day menu including breakfast, lunch and dinner, which tells her exactly what to buy. Prosser uses sales fliers to help plan her meals.

Step Four -- Shop, Save

The key to cutting your grocery bill in half is to use multiple coupons for items on sale. Most grocery stores will double coupons up to $1 or more, and some stores occasionally triple coupons.

If an item is not on sale, or if she doesn't have a coupon for it, Prosser doesn't buy it. It's important to stick to your grocery list, and try to avoid the bakery and deli sections. Those delicious-smelling foods can blow your budget fast.

Prosser said it helps to eat a good meal before stepping foot in the store.