Once a month, I fold down the seats of my minivan and head to that most magical of shopping meccas, Costco. The warehouse club has everything my family of seven needs and at prices that can almost never be beat. Giant bags of chips for the same price as a small bag at the supermarket? Yes, please. After years of shopping at Costco, I’ve fine-tuned my shopping strategies, but not before making a few mistakes first. Here are nine gaffes you’ll want to avoid yourself. 1. Sticking with Kirkland Signature products Don’t get me wrong. There are plenty of Kirkland Signature products that offer great value and quality. However, Costco’s house brand isn’t always the best deal. 2. Assuming you need a membership While a membership gets you all the deals, there are actually a number of ways to shop at Costco without paying a fee. These include shopping online, filling prescriptions and, in some states, buying alcohol. 3. Only buying goods Sure, your local Costco location can rotate your tires, but there are so many more discounted services available that you may be missing. These include insurance products, identity theft monitoring and your next dream vacation, as we detail in “18 Surprising Things You Can Buy at Costco.” Next time you’re in the store, pay attention to the display by the customer service desk to see more of what’s available. 4. Sticking with the cheaper membership You may already be a little iffy about paying to shop somewhere, but you could be making a mistake if you stick with the regular membership. While the executive membership costs twice as much — $120 per year — it comes with 2% cash back on all your purchases, up to $1,000 a year. That means if you spend at least $500 a month at Costco, the more expensive membership pays for itself. 5. Missing out on sales Costco offers monthly member-only savings on a variety of items both online and in their warehouses. While the retailer sends member-only savings booklets in the mail, you can easily see those discounted products online as well. It pays to check these out before heading to the store because some sale items can be tucked away in the aisles and aren’t prominently displayed. 6. Shopping on the wrong days Weekends are notoriously busy, and you could find yourself in a sea of people all jostling to buy the same items that are on your list. I’ve also been told by employees that the start of each sale cycle is when crowds swell to their largest. Shopping on weekdays or later in the sale cycle is your best bet for enjoying a quiet store. There is also often a week between sales periods and that can be a good time to stock up on purchases that don’t go on sale. To find out Costco’s current sale cycle, check the member-only savings book that Costco mails out or visit the retailer’s member-only savings webpage. 7. Never shopping online If you’d rather not fight the crowds, many warehouse sale items can be bought online for a slightly higher price. Plus, Costco has many online-only deals for members. I tend to shop Costco’s website most often during the holidays. The website offers affordable gifts, and, as an executive member, I get 2% back on all my purchases. 8. Not buying gift cards Costco offers significant savings on gift cards. For example, my local warehouse sells $100 worth of gift cards to a local theater for $75. There are also restaurant, retail, gaming and travel gift cards to be found in stores and online. 9. Forgetting the return policy Fortunately, if you do buy an item that leaves you less than impressed, you can generally return it for a full refund. That’s thanks to Costco’s Risk-Free 100% Satisfaction Guarantee. Don’t make the mistake of overlooking this money-saving perk.