4 Amazon Prime Mistakes You May Not Even Realize You're Making

An Amazon Prime membership costs $139 a year. In exchange, you get access to a host of benefits, like free unlimited fast shipping and access to streaming content that extends to movies, TV, music, and books.

But if you're not careful, you might run into certain pitfalls in the course of utilizing your Prime membership. Here are some blunders you should really take steps to avoid.

1. Choosing the fastest shipping option when you don't need it

For many Prime members, it's the fast free shipping that makes the program's $139 annual fee worth paying. But that doesn't mean you have to take advantage of free one- or two-day shipping all the time.

Amazon will commonly issue promotional credits you can redeem for digital purchases if you forgo the fastest shipping and opt to wait longer for your orders to arrive. So if you're buying something you don't need right away, then it pays to adjust your shipping options accordingly. You can redeem your promotional credits for things like books to read on your Kindle or movies you'd otherwise have to pay to purchase or rent.

2. Using the wrong credit card when you shop

Storing your credit card information on Amazon could make your shopping more convenient (though be careful, because in some cases, it could also lead to overspending). But it's important to use the right credit card so you're maximizing your cash back.

The Prime Visa, for example, offers 5% back on all Amazon purchases. That also extends to AmazonFresh and Whole Foods.

Now you may have another go-to credit card you prefer to put purchases on. But unless it's giving you 5% back across the board, there's a good chance the Prime Visa is a better choice for your Amazon purchases.

3. Not signing up for Subscribe & Save

Many of us have items we buy from Amazon on a regular basis. If that's the case, then it pays to sign up for Subscribe & Save. Doing so allows you to not only automate your shipments, but snag a discount on the items you're buying. It's a win-win.

And you don't have to commit to a preset schedule, either. Amazon will usually send you a reminder to review your Subscribe & Save orders each month, so if there's an item you no longer need, you can simply cancel it without penalty. And, you can choose the frequency at which you have items delivered so that certain items arrive monthly and others arrive once every three months.

4. Not shopping around on other sites

Because Amazon's prices are quite competitive, it's easy to assume you're getting the best deal regardless of what you're buying. But it may be the case that another retailer has a better deal going on, so if you're making a larger purchase, it's always good to shop around.

For example, right now, Amazon is selling the Fitbit Charge 5 for $149.95. Walmart, however, is selling it for $146.95. And while that's only a $3 difference, why pay more if you don't have to?

You may feel that your Amazon Prime membership is more than worth the money. But it still pays to avoid these mistakes if you can, to maximize your benefits.