Shop with a list; compare the per-unit cost; scour the sales circulars. Been there, tried that. I still waltz out of Target with bags full of stuff that I didn't intend to buy.

It's no wonder: Two-fers, upgrades, bulk buys, bonus points, door-buster deals -- they're like magnets for our money.

Costco has the formula down pat. In a Motley Fool interview, CEO Jim Sinegal copped to purposely merchandising to the impulse-purchase mind-set. Costco highlights an ever-changing array of items at the entrance -- from Coach handbags to Fila track suits -- that are probably on no one's shopping list. Yet they end up in a lot of customers' shopping carts. Sinegal explained, "The attitude is that if you see it, you have got to buy it, because it may not be there next time."


So how do you resist the pull of blue-light specials and expertly orchestrated merchandising? Let's start by talking about your relationship with your mother.

Start shopping smarter
We're only slightly kidding with that "mother" crack. If you want to steer your shopping cart -- and your finances -- in the right direction, you really do need to explore the mind-money connection. Marketers certainly have.

But you can resist those retail brain-benders. The next time you reach for your wallet, try one of these five mental money tricks to help you walk away from the checkout counter with no regrets -- and a fatter wallet.

1. Ignore the source of your spending money
Every dollar is worth a dollar, no matter whether it comes from an ATM, a great-aunt, or the laundry hamper. Yet people show less restraint with so-called "found money" (tax refunds, work bonuses, and inheritances) than they do with funds they earned (paychecks and babysitting money).

A little accounting amnesia can work wonders for those who tend to blow through windfall cash. The authors of one of my favorite books -- Why Smart People Make Big Money Mistakes -- suggest banking found money for a while before spending a dime. Mingling the dough with money you worked for mentally converts the cash into "savings." And you're less likely to treat savings like loot won with a scratch-off ticket.

2. Sweat the big stuff
Oddly, we're more thoughtful with large-sum unexpected windfalls than we are with smaller amounts. However, many people have a blind spot when it comes to spending earned money on big-ticket items.

According to those surveyed for the book Are You Normal About Money?, just 8% of us price out a vacation before we hit the road. Yet the average trip tab -- around $2,300 -- amounts to about 8% of the average American's annual income.

In everyday shopping terms, it's like spending 20 minutes a week to find the gas station charging $0.02 less per gallon, but not even bothering to negotiate the price of the car you're filling up.

Consider the biggest slices of your spending pie, and practice cost-consciousness where it counts: vacations, transportation, holiday and home expenses, or cosmetic dentistry. Comparison-shopping in these categories can save you some serious cash.

That said, don't dismiss those seemingly small money decisions outright. A few percentage points of interest on your credit card or checking account, or paying a few bucks more per stock trade, may not sound like much, but they add up.

3. Comparison-shop with skepticism
On the lookout for rock-bottom prices? Put on your blinders. In an oft-cited experiment by two Berkeley business school professors, shoppers given the choice between two microwaves -- a low-end and midrange option -- split nearly equally down the middle, with 43% choosing the more expensive oven. But when a pricier alternative was added to the mix, the majority of shoppers (60%) decided the mid-range microwave was the best deal.

Academics call this "extremeness aversion" -- wary of alternatives at both ends of the price spectrum, even the bargain hunters decide to trade up. The resulting budget creep occurs on everything from cars to cameras to coffee.

To avoid this Jedi money mind trick, stay focused. Weigh the merits of each product independently. Pick your must-have features and a target price range. Compare like with like -- and erase from your mind the alternatives that don't fit your criteria.

4. Keep separate tabs
"What's another $[fill in the blank] when I'm already spending $[fill in the blank]?" Contractors, car salesmen, and electronics store clerks bank on this kind of faulty thinking. In the context of a larger purchase, somehow $300 cup holders and $3,000 Corian countertops start to make sense.

Don't let upgrades and add-ons pad your tab. Instead, consider each option separately, and ask yourself if you'd pay $[fill in the blank] were you shopping solely for that item.

5. Leave home without your credit card
It's easy -- too easy -- to pay with plastic. That's why the price of credit card convenience is higher than that of cash. Yes, even if you pay your credit card bill in full every month.

Studies show that people spend more -- and more stupidly -- when no actual cash changes hands. We succumb to impulse buys (an estimated 59% of grocery store purchases are not planned) and even tip more at restaurants when we put the tab on plastic.

Smart People/Big Mistakes authors Gary Belsky and Thomas Gilovich say that plastic makes us devalue what we spend because we don't experience the immediate loss of buying power that we do when we pay with cash. Like Vegas gambling chips, credit cards mask the tangible aspects of spending money. (Quick gut check: Visualize the difference between handing the cashier $40 of the $80 in your pocket versus putting it on your card. Feel the pain?)

Pay only in cash, and you'll likely see a dip in your daily expenditures. Imagine the results after an entire year. Now that's a rewards program Visa and MasterCard can't match.