Avoid these pitfalls to get the most from your next trip to Costco, Sam's Club or BJ's. By Andrea Browne Taylor, Online Editor January 2016 There are savings to be had at warehouse clubs. But there are plenty of ways to overspend, too. Avoid these costly mistakes and you’ll come out ahead.See Also: Worst Things to Buy at Trader Joe's Let’s start with the basics: Buying in bulk is great as long as you use up everything before it spoils or expires. Check the dates on packaging, and freeze items that’ll keep, such as meats. Also, be sure to compare unit prices, such as cost per ounce, rather than package prices. Otherwise, you might pay more per unit on bulk purchases even though it seems like you’re getting a good deal. No matter the package size, canned goods and sodas are almost always cheaper during supermarket sales. Finally, here’s a trick you probably don’t know: Skip the center aisle at warehouse clubs. This is where impulse buys such as DVDs and toys are displayed. To be safe, always shop with a list—and stick to it—to avoid temptation. There are more costly shopping mistakes at warehouse clubs that you are probably making. Plus: Learn about the worst things to buy at Costco, Sam's Club and BJ's.