Editor’s note: An award-winning journalist, author and motivational speaker, Jean Chatzky needs no introduction. As a financial editor for NBC’s "Today Show," Chatzky offers savvy advice on managing money and wealth. Her latest book, The Difference, provides simple strategies for a prosperous financial future. Visit her blog at JeanChatzky.com.

The first time I shopped at Costco, I bought three bathing suits for my daughter, a set of 50 (maybe more) magic markers and a box of Ring Pops so large even my children got sick of eating them. My husband, Eliot, went me one better. He bought a tent.

Did I mention we had no intention of buying these things?

Did I mention that my daughter is of the age where my picking out her clothes is no longer acceptable?

And did I mention that the register receipts set me back a few hundred dollars?

Turns out I’m not the only one. A study by Michael Norton, assistant professor at Harvard Business School, and Leonard Lee, assistant professor at Columbia School of Business, points out that many people do exactly the same thing. Why? The membership fees you pay to belong to warehouse clubs – like Costco, Sam’s Club, BJ’s – make people think they are getting better deals. In fact, they often are. But those deals often make you buy more (in my experience sometimes much more) than you need.

Which is why for about three years, I refused to step foot in one. I didn’t want to be tempted by vats of juicy blueberries, bestsellers that would stack up on my nightstand, newfangled phones. But then I got married and Eliot – despite the tent fiasco – is a Costco fan.

So, we re-upped, this time with ground rules. We went to the store with the understanding that we would buy absolutely no food. We wouldn’t even walk down the aisles that contained food. I broke that rule in about five minutes shoving a bottle of Kirkland Extra Virgin Olive Oil (it was ridiculously cheap!) into the cart. We bought Ziploc bags, paper towels, toilet paper, cleaning supplies. We loaded up on paper plates for summer barbeques, napkins and batteries. With each purchase, we asked ourselves the questions: Do we need this? Will we use it up? And with that as a guideline, we still managed to spend $300. But we didn’t feel nearly as bad.

It’s been three months since then … in fact, maybe four. I still have enough baggies to last through the lunch-making months of the school year, but I’m running low on olive oil and I’m out of Tide. Clearly another Costco run is in the offing. I recently opened the lines on my radio show to see if any listeners had suggestions of other ways to get abargain while keeping my desire to get all the bargains in check. They did:

From Heather who shops weekly at Costco and her local grocery store: "I’ve checked the unit prices of the items I buy most often at both places. So I know – for sure – that the big box of goldfish crackers at Costco ($6.97) would cost $9 or $10 at the supermarket. Dog food is cheaper too."

From Lisa, who used to shop at Sam’s Club itself but has recently gotten addicted to the store’s online, late-night auctions at Sams.com: "I recently got such a good deal on an iPod dock that I bought three. I gave one to my son. One to my daughter. Did I need three? Um, no. But they were such a bargain I couldn’t resist."

From Glenn, who went into Costco last week for barbecued ribs and came out $190 later with bottled water, beer, paper towels and – oh yes – an organizer for his electrical cords: "I’ve been told [by my wife] there are certain aisles I’m not allowed to go down anymore."

Do any of you have warehouse shopping stories (tents?) or strategies (lists?) you’d like to share?