Avoid overspending by sticking to a list, skipping the center aisles and more. Plus: Beware free samples. Thinkstock By Cameron Huddleston, Former Online Editor March 9, 2015 Low prices are the big draw of warehouse clubs, such as Costco, BJ’s and Sam’s Club. That’s why many consumers turned to these mega-stores during the recession, according to IBISWorld, which provides industry analysis. But it’s not just during tough times when consumers stock up at warehouse clubs to take advantage of discount pricing. These bulk-goods chains have seen rapid growth over the past decade and their share of the retail sector is expected to continue to grow, according to IBISWorld. SEE ALSO: What Not to Buy at Warehouse Clubs There certainly are savings to be had at warehouse clubs if you shop smart. But there also are plenty of ways to overspend. For starters, you have to pay $45 to $55 to become a member of Costco, BJ’s or Sam’s Club. Although prices are low on many items, you might not be saving enough by shopping at a warehouse club versus other non-warehouse stores to compensate for the membership fee – especially if you’re making these seven costly mistakes. Shopping without a plan. Walking into any store without a list of what you need to buy is a mistake. But the omission can be especially costly at warehouse clubs because these retailers sell such a wide array of products in such large quantities that you might be tempted to buy – even if you don’t need them. Plus, warehouse clubs often set up stands throughout their stores to offer samples of food items that are sold there. If you walk in without a list and get tempted by the samples, you will likely end up making a lot of impulse purchases, says Lauren Greutman, a grocery shopping expert and founder of IAmThatLady.com. An even worse move is buying a warehouse club's super-size version of an item you've never tried, only to get home and discover you don't like it. Assuming you’re getting the best prices on everything. You can find huge savings at warehouse clubs, Greutman says, but just as often you can waste your money. That’s because many items sold in bulk at a warehouse often are cheaper per unit when sold in smaller packages at the supermarket – especially when those items are on sale. For example, you can pay 20% to 40% less per unit on canned goods when they’re on sale at the supermarket than what you pay for a super-size container at a warehouse club, says Teri Gault, CEO and founder of TheGroceryGame.com, a grocery savings Web site. Cereal, eggs and soda are among the other items that are usually cheaper at the supermarket. See What Not to Buy in Bulk for more. Advertisement Counting on manufacturers' coupons. If you’re a fan of clipping coupons, don’t assume you’ll always be able to lower the price of your warehouse club purchases even more by redeeming them. Some warehouse clubs including Costco and Sam’s Club do not accept manufacturers' coupons. BJ’s does accept them, plus it offers its own coupons. Costco also offers its own coupons. Forgetting to factor in waste. Even if the price per unit for an item at a warehouse club beats the price at other retailers, you still have to consider whether you’ll be able to use up the large amounts sold in bulk at clubs, Greutman says. For example, if you live alone, buying a huge box of organic lettuce may not be the best option. And produce isn't the only thing that can go bad quickly. Some pantry staples such as spices and cooking oils also have a relatively short shelf life. You aren't actually saving money if part of a purchase ends up in the trash, Greutman says. Failing to team shop. You can still take advantage of deals at warehouse clubs without worrying about waste even if you don’t have a big family. Just find a friend, relative or neighbor with whom you can split bulk purchases, says Kyle James, founder of Rather-Be-Shopping.com, a coupons Web site. This will allow you to take advantage of warehouse club savings without having to worry about items going bad or whether you have enough room in the freezer. Shopping the center of the warehouse. The center aisles of most warehouse clubs are full of stuff you had no idea you needed but clearly cannot live without, James says. You could easily spend an extra $50 to $100 if you wander into these aisles that hold everything from books and DVDs to toys and children’s outdoor playsets, says James, who has made this mistake himself. “Stay out of this danger zone unless you are shopping for something specific,” he says. Advertisement Rushing into a membership. Just like joining a gym, it's a waste of money to join a warehouse club if you never end up stepping foot in it. You can try out warehouse clubs before you commit to – and pay for – a membership. Both BJ’s and Sam’s Club offer a free one-day pass. However, you’ll have to pay a 10% to 15% surcharge on purchases without a membership. Costco will allow you to shop at its stores without a membership if you have a Costco Cash Card gift card (which you can ask a friend who is a member to buy for you), Greutman says. Plus, warehouse club pharmacies are open to the public, so you can get prescriptions filled without being a member. And you’ll likely pay less for prescription drugs at a warehouse club than at a drugstore (see What Not to Buy at Drugstores for more).