I Shop at Costco Every Week. Here Are 3 Mistakes I Still Make

I've been a Costco member for more than 15 years, and for much of that time, I've had an executive membership. The executive membership costs twice as much as a basic one -- $120 versus $60 -- but in exchange, I get to snag 2% cash back on my Costco purchases, so the higher fee is worth it to me.

Not only have I been a Costco member for a long time, but I tend to shop there on a weekly basis. Doing so helps me save money on everything from packaged food items to fresh produce to household cleaners and products.

But while it's safe to say I'm a pretty seasoned Costco shopper, I still manage to make my share of mistakes in the course of shopping there. Here are some pitfalls I commonly fall victim to that you may want to avoid.

1. Not trying the samples

Because I have a busy schedule, often, when I shop at Costco, my goal is to get out as quickly as I can. As such, I'll often forgo the free samples because I don't want to waste time seeking them out or wait behind other shoppers to get my free cracker and cheese. But actually, there are times when I've missed out on trying some pretty great products by forgoing the free samples.

Recently, a friend told me she tried a delicious hard cheese at Costco and had scooped up a block of it on sale. Chances are, I could've tried that cheese, too. And had I liked it, I could've bought it that same week on sale. By the time I went to pick up a block based on my friend's recommendation, that cheese was no longer available at a discount.

2. Giving in to impulse purchases

Shopping at Costco can open the door to lots of temptation. And no one knows that better than me.

Whether it's a fun-looking snack item or a yummy baked good I've never seen before, I have a tendency to throw random Costco items into my cart without really stopping to think about whether I need them or ought to be buying them. As a result, I sometimes spend more money than necessary at Costco, which is ironic since the main purpose of shopping there is generally to save money.

3. Not checking prices elsewhere

Because Costco offers such competitive prices, I'll often operate under the assumption that it's apt to have the lowest price available. But that's not always the case.

The problem is that because I'm often in such a rush when shopping at Costco, I won't stop to spend three minutes using my phone to compare prices at other retailers. For example, if I need paper towels, I'll just buy them at Costco even if they might be on sale at Target for a lower price.

Now to be fair, since I'm self-employed, not having to drive to another store not only saves me time, but helps me earn money by sparing me an errand and allowing me to work more. So often, it's worth it for me to spend a few extra dollars here and there if it frees up working hours. But still, I'm really not good about comparison-shopping when it comes to Costco purchases, and that's a habit I know I need to break.

Clearly, many of my Costco blunders boil down to rushing through the experience. So perhaps what I really need to do is to carve out more time in my schedule to do my Costco shopping. But either way, I'm sharing these blunders in the hopes of helping other people steer clear.