Memorial Day weekend kicks off the summer shopping season as retailers look to unload their spring merchandise.

The three-day weekend is one of the biggest shopping holidays of the year, second only to Black Friday, the day after Thanksgiving, in terms of the bargains available.

Savvy shoppers would be wise to pick their battles, splurging on items where savings are the greatest and avoiding other categories where deals can be had later in the year, Vera Gibbons, senior consumer analyst at GasBuddy.com, told CNBC’s “On the Money.”

You should worry less about the differences between in-store and online deals because they are generally similar, Gibbons said.

But if you go to brick-and-mortar stores, be sure to keep the notifications for your favorite retail apps turned on because there might be some in-store offers to take advantage of, said Brent Shelton, online shopping expert for FatWallet.com.

Your phone will come in handy at check-out, too, because many stores will match prices offered online by their rivals, Shelton said.

Memorial Day sales bring out the bargains for a grab bag of categories:

Mattresses: “This is the best time of year to buy a mattress,” said Benjamin Glaser, features editor at DealNews.com. Don’t accept anything less than 50 percent off and you should push for more discounts if you can, Glaser said.

Spring apparel: Clothing sales account for roughly 40 percent of all Memorial Day purchases, Gibbons said. You can find discounts as much as 90 percent on clothes as retailers are desperate to clear out their backlog. “It’s the perfect time to buy a light sweater,” Glaser said.

Appliances: Most manufacturers roll out their new models of ovens, refrigerators, washers and dryers in the summer. That means retailers, like Home Depot, Lowe’s and Sears are willing to offer discounts as much as 50 percent to move the old models off the floor, Gibbons said.

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Deals are tougher to come by this weekend for certain items:

Summerwear: The big sales for swimsuits and sandals happen over the Fourth of July weekend. “You may find some markdowns now, but not the best,” Gibbons said.

BBQ grills and patio furniture: Hold off on making your backyard paradise. Gibbons recommends waiting after the Fourth of July for the biggest deals on these items.

Electronics: Retailers may cut you some slack this weekend, but the greatest discounts appear in late June as stores clear out their inventories for the back-to-school shopping season. “Now is not the time to buy that flat-screen TV,” Gibbons said.

“On the Money” airs on CNBC Saturdays at 5:30 a.m. ET, or check listings for air times in local markets.