3 Common Mistakes Made by First-Time Costco Shoppers

Every new Costco member makes a few excusable mistakes, like putting big items on conveyor belts in checkout lines when veterans know to leave them in the cart. But some mistakes will cost you more than just wounded pride.

Take heart, new member. If you're about to make your first trip to Costco -- or did but are wondering what went wrong -- be on the lookout for these three common mistakes.

1. Buying brand names

Yes, Costco has amazing deals on brand names and very seldom do other stores beat its prices on the same products. But the secret juice to saving money at Costco is indisputably, uncontroversially buying Kirkland Signature products in bulk.

For those who, like me, grew up eating generic brands of cereal and carried off-brand Lunchables to school, make no mistake -- Kirkland Signature is not inferior to brand names. In fact, many are well-known superheroes disguised under the Kirkland brand. For example, some Kirkland coffees are made by Starbucks, and its cranberry juice is Ocean Spray.

These products are your bread and butter in saving money -- metaphorically, but also literally because Kirkland butter is great and super cheap. One Kirkland product I love is the shelled pistachios. For $15, I can buy a 1.5 pound bag (24 ounces) bag. That's less than half the price of buying the same quantity of Wonderful Pistachios from my local Safeway ($7.99 for six ounces).

So skip the brand names. It's going to work wonders for your finances.

2. Getting the wrong membership

Costco offers two annual memberships: Gold Star for $60 and Executive for $120. And while there are several differences between the two, the big difference is that an Executive membership earns 2% cash back (up to $1,000 in earnings) and a Gold Star doesn't.

Now, I get why you would feel hesitant to buy an Executive membership. After all, you're trying to save money. Why not start this Costco thing with a savings of $60 and choose the Gold Star membership?

Truth is, most Costco shoppers will spend enough to justify getting the Executive membership. The magic number here is $250. If you can spend $250 per month ($3,000 per year), you'll earn enough to cover the difference between the two memberships, or $60. If you can spend that, it's worth getting the Executive membership.

Now, if you really want to earn cash back, you could also get the Costco Anywhere Visa Card. This rewards card earns 2% back on Costco purchases, but when combined with the Executive membership, you can earn 4% back. That's really good and can compete with some of the best grocery credit cards.

3. Paying full price for certain products

The more frequently you shop at Costco, the more you'll notice how certain brands and products are the headliners for sales and promotions. A rookie move, then, would be to buy these products at full price, rather than wait until they're discounted.

For example, Costco frequently runs promotions on its electronics, whether that's televisions, laptops, headphones, speakers, or smartphones. It also has seasonal promotions on furniture -- both indoor and outdoor -- and on kitchen appliances. Tires are another favorite sale item, as are mattresses -- which often come with a $150 to $200 Shop Card during a promotion.

The point: Be on the lookout for the products typically on sale at your local warehouse. While you can't always time a purchase exactly right -- tire purchases, for instance, might be difficult -- you can stop yourself from paying full price for items that can wait.

That said, if you purchased something at full price before it goes on sale, Costco may credit you the difference. The retailer has a price adjustment policy that will reimburse if you request the adjustment within 30 days of your purchase. So if you bought an air fryer for $100 right before it went on sale for $60, Costco would give you $40 back.

All in all, making a mistake at Costco boils down to saving less than you could have with the right knowledge. But by buying Kirkland Signature products, getting the right membership, and paying attention to sales, you'll squeeze more value out of your Costco membership. You might not know all the ins and outs of Costco yet -- such as how to avoid Costco traffic -- but you'll be saving money, which is what Costco veterans do.