To save on groceries, you gotta bust out the coupons. And before you do that, you gotta bust these four coupon myths that might otherwise discourage you from getting all the deals you deserve, Susan Samtur, the original "Coupon Queen," told Savannah Guthrie this morning on TODAY.

Myth 1: "A one-dollar coupon is always more valuable than a 75-cent coupon."

Busted! It's not just about the face value of the coupon. Check the fine print. If the store is offering double coupons on the 75-cent coupon, now it's worth $1.50, beating out the dollar coupon.

Myth 2: "The generic brand is always cheaper than the national brand."

Busted! Samtur snagged a box of Cinnamon Toast Crunch and used a dollar coupon to get it for 88 cents, versus $3.79 for a generic box of "Cinnamon Toasters."

Myth 3: " There are never coupons for fresh foods."

Busted! This one is tricky because it didn't used to be a myth. "Manufacturers have come to learn people aren't looking for coupons just for processed items, they're looking for fresh stuff," said Samtur." You can get fresh fruits, vegetables and eggs with brands from big companies, and the coupons to go along with them.

Samtur showed off how she got two cases of "Egg-land's Best Eggs," for "cheep." Retail price: $6.98. After coupons? 98 cents, 49 cents per dozen. "We bow down!" said Guthrie, pretending to genuflect before the 4"9.5' tall "coupon queen."

Myth 4: "If a deal looks too good to be true, it probably is."

Busted! Samtur saw a jar of Mt. Olive pickles in the circular on sale for $1.98. Then, when she went into the store, there was a tag on it offering $1 off if you bought two. Combining the two deals, she got two jars of pickles that regularly go for $6.98 for the low price of $2.98. Now that's a deal worth bending your knee for.

To catch more of Susan Samtur, check out her appearance on TLC's Extreme Couponing tonight.

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The study found that store displays can get female shoppers to change their preplanned purchase decision from their favorite brand to another product.

You make your shopping list, download some coupons from the Web and head to the supermarket. You’re ready to be a frugal shopper. And yet there’s still a good chance you’ll make a significant number of impulse purchases.

An overwhelming portion of the average shopper’s purchasing decisions -- 76 percent-- are being made in the store, according to the recently released 2012 Shopper Engagement Study. That’s an all-time high for this sort of survey.

“What you find is that people will tell you they plan to do one thing, but their actual behavior will be quite different,” says Richard Winter, president of Point of Purchase Advertising International, the marketing association that conducted this survey.

Researchers interviewed 2,400 shoppers as they were about to start shopping and afterward. 

“While a person would enter a store and anticipate things on a list that they planned to purchase, the actual purchases changed while they were in the retail environment,” Winter says. 

The study found that store displays can get female shoppers especially to change their preplanned purchase decision from their favorite brand to another product. It seems a company can do all sorts of marketing, but the real decisions are made while the customer is shopping. 

Brian Wansink, director of the Food and Brand Lab at Cornell University, says deviating from the shopping list can be costly. 

“If you’re making impulse purchases, it’s likely you will spend more than you planned,” he says. 

Pay with cash if you want to spend less
According to the Shopper Engagement Study, people who pay with credit cards or debit cards are more susceptible to impulse purchases. They buy larger quantities and make more unplanned purchases than those who pay with cash. 

“I think there’s something about having to shell out cold, hard cash that makes you more cautious about how you spend,” says Gerri Detweiler, a personal finance expert with Credit.com. 

Besieds, most shoppers can’t accurately predict how much they will spend at the store. The average shopper in the engagement study misjudged how much he or she would spend by 35 percent. More than half (57 percent) spent more than planned.

One more interesting finding
Researchers were surprised to see that a significant number of people left the store without buying everything on their list. It could be that these shoppers simply forgot those items. Or more likely the price was not as good as they expected, so they decided to skip the purchase and try another time.