Join If: You're looking for a regular bargain on anything from bulk groceries to electronics to tires to computers. For those who can't use the giant-size food packages the stores are famous for, the discounts these stores offer on auto and home insurance and financing, long-distance phone service, prescriptions, gasoline and propane, and travel services may make membership worthwhile.

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Costco
With 452 stores in 36 states and six countries, this is the biggest warehouse club in total sales. The standard Gold Star membership costs $45 a year and comes with an extra card for a spouse. For more information, go to www.costco.com or call 800-774-2678.

Sam's Club
This division of Wal-Mart runs nearly 540 stores in 48 states. The standard Advantage membership costs $35 a year and includes membership for a spouse or another family member. For more information, go to www.samsclub.com.

BJ's Wholesale Club
With only 154 stores, mostly in the Northeast, this is the smallest of the three major clubs. Still, its stores generally have a larger selection than Costco or Sam’s Club, with a focus on food, which accounts for more than half of all sales. The standard Inner Circle membership costs $40 a year and is good for two members of the same household. Go to www.bjs.com to learn more.