When there are limited ways to increase your income, cutting expenses is the key to balancing the books.

I've written recently about federal tax credits for retirement contributions, ways to get free airline tickets and tricks to slash hotel and restaurant bills.

There are countless ways to save money, but every now and then there's a store promotion that I find myself telling all my friends about, and I'm going to share one of those.

It's one of those rare promotions that allows you to put cash in your pocket simply by buying things you were going to purchase anyway: groceries.

Follow the rules, and over the next three days you could collect up to $60 in gift cards (this promotion runs through Aug. 31).

Here's how it works:

Piggly Wiggly stores are running two deals that together allow shoppers to collect an unusually large amount of the reward points known as Greenbax, and then cash them in for gift cards to a variety of stores.

You need to have a "Pig Card" from the chain's loyalty program to participate, but they're free at the customer service counter if you don't have one.

Today through Tuesday, you can collect up to 10 extra Greenbax each day by using up to 10 coupons when you shop: one Greenbax for each coupon you redeem. It doesn't matter what the coupon is worth, or the price of the item purchased.

Through Sept. 7, you can trade in Greenbax for gift cards. Just pick out an appropriate card at the grocery store, and pay for it with the Greenbax electronically stored on the Pig Card.

The 10 Greenbax you can get each day for using 10 coupons are enough to pay for $20 in gift cards. Do this three days in a row, and you can pocket $60.

This is a no-brainer for me because The Post and Courier is practically across the street from a Piggly Wiggly.

I headed over there a few days ago, picked up eight things I needed, and used coupons from last week's Sunday paper to buy each of those items.

Here's how that worked out: Those coupons knocked my bill down from $24 to $18. The Greenbax recorded on my Pig Card for using eight coupons can be redeemed for a $15 gift card.

My net cost for $24 in groceries? Three dollars, plus tax.

As I've said in previous columns, saving money often requires taking a little extra time and paying a little extra attention, in this case clipping coupons, signing up for a Pig Card and making multiple trips to the store.

For some, this sort of trade-off may not seem worth it. For others, such as the countless people in our area who have lost jobs or have seen their pay reduced, it can be an important piece of the puzzle in making ends meet.

There's another grocery store promotion ending Tuesday that's of particular interest to people east of the Cooper.

Through Aug. 31, the new Harris Teeter in Mount Pleasant is offering a $20 store credit for members of their VIC Card loyalty program who fill a new prescription there. If you have a prescription that needs filling, why not get $20 back?

Know of any great ways to save money? Send me an e-mail, and I'll check it out.

Reach David Slade at 937-5552 or dslade@postandcourier.com.