3 mistakes to avoid on Prime Day, according to shopping experts

Amazon's annual Prime Day sales event is here, with the e-commerce giant advertising some of its "lowest prices ever" for subscribers who pay for its $139 annual membership program.

The event has become a July version of Black Friday, and other retailers have introduced their own sales to compete with Amazon. It's a great opportunity for shoppers to score good deals on products they've been meaning to buy.

But not all Prime Day sales are created equal. The best value to be found is on Amazon's own products.

"On Prime Day, what you will see extremely well discounted is anything Amazon branded," Nathan Burrow, a senior deals editor at Wirecutter, tells CNBC Make It. "That extends not only to Amazon's smart devices like the Echo or Kindle Paperwhite, but to things that folks might not even know that Amazon owns, like Eero mesh routers and Ring doorbells."

Beyond that, to find the best deals during Prime Day, Burrow says "you need to take a diligent approach." There are common mistakes that can result in not getting the best bang for your buck.

Here are three missteps to avoid to make sure you get the best value out of Prime Day.

Prime Day is center of the summer deals calendar, but it's not the only star.

"There are so many retailers that have competing sales," says Julia Ramhold, a consumer analyst at DealNews, pointing out that Target, BestBuy and Costco also have sales events this month. "Even if you have Prime, I would say look at other retailers. It may be that you can get something sooner or can get a better price."

Both Ramhold and Burrow say that shoppers shouldn't buy anything from Prime without first checking Amazon's competitors.

"Know that there are a lot of options out there for you," Burrow says. "The more options you have, the more choices you have. [And you have] more capacity to verify the deal is good."

On Prime Day, price isn't the only factor you should consider when deciding whether to not to make a purchase, Burrow says.

"We recommend not only vetting the sale, but also vetting the product," he says. "A deal isn't a deal if it's a bad quality product."

He says that the Amazon website is engineered to get consumers to spend as much as possible, and shoppers should be prepared to handle that.

"The inventory bar that shows you the inventory rapidly disappearing, or the time running out to get a deal, I think that can create a false sense of urgency in some cases," Burrow says. "Folks have a tendency to mash that buy button without necessarily doing their due diligence."

Instead, Burrow recommends creating a shopping list on the site of the items and sales you are already interested in. That way, you can research those items without getting distracted by other offers.

Ramhold also says buyers should be aware of Amazon's tempting Lightning Deals, which advertise Prime-exclusive discounts on a product for a set amount of time. These discounts can be misleading, however, because they reflect the price cut from the list price, rather than the usual price on the site.

"Amazon rarely charges list price," she says. "It's a little bit misleading in the fact that you think you're going to be getting a bigger discount on top of the already normal discounted price, and that's just not what it is."

While an item may be on sale during Prime Day, that doesn't mean it's necessarily going for the best possible price.

Both Burrow and Ramhold recommend using sites like CamelCamelCamel or Keepa to view the price history of the products you are interested in. The additional information might show that the product sees even steeper discounts during the holiday season, for example.

"You can save yourself some serious buyer's remorse and you can generally tell whether or not the so-called deal is a real deal," Ramhold says. "Is this really the lowest [price] it's been?"

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