Big discounts, freebies from Costco, Sam's Club and 4 other memberships (that most don't know about)

On an average week, Americans spend $134 more than they planned to, according to research from shopping platform Slick Deals. If you're looking for ways to cut costs in your day-to-day life, opening your wallet and going through your membership cards can be a smart way to start.

Memberships to organizations like AARP or your local library offer a variety of little-known discounts and freebies. Here are four that can easily help you save money:

The cost of joining AAA can be as little as $21 a year based on where you live and what kind of coverage you have. The organization has more than 58 million members, so it's possible you already have a membership card in your wallet.

While you might join for roadside assistance, AAA also offers discounts on travel-related expenses, says Kristin McGrath, a shopping expert at Offers.com. For example, many hotel chains offer a discount of $5 to $10 per night to AAA members.

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You need to show your card to score the deals. "I once forgot to bring my AAA card and was promptly switched to the full-price rate at check-in for all nights of my four-night stay," McGrath says. "So don't forget your card at home."

If you search AAA's discount portal, you'll find deals on lots of other purchases, too. This includes 10% off at certain restaurants. "Some particularly good offers we've seen include 20% off Samsonite luggage and 35% off HP products," she says.

"AARP has one of the most robust selections of discounts out there for its members," McGrath says. And although many people believe you must be older to join, you can actually get an AARP card at any age. That means you can take advantage of these discounts at any age. Roger Ma, a certified financial planner at Life Laid Out, told Grow he joined AARP at age 35 and saves $200 to $300 per year using his membership.

An AARP membership costs as little as $12 your first year and $16 a year after that. With it, you can get deals like 10% to 25% off car rentals from Avis and Budget Rent a Car, and up to 20% off ticket prices at Regal.

Many chain restaurants also offer discounts: AARP members can save 15% at Denny's, and 10% at Outback Steakhouse, Bonefish Grill, and Carrabba's Italian Grill, among others.

Local libraries often have more to loan out than just books. Fishing rods are one of the Chicago Public Library's most frequently checked out items. Libraries in Philadelphia, Sacramento and Phoenix all loan out instruments.

If you need to use Photoshop, a 3-D Printer, or other pricey technologies, you might want to see if your library has them on-site. The Houston Public Library and Los Angeles Public Library both have creative labs where you can use Adobe Creative Cloud products. Some libraries also have sewing machines and craft cutting machines.

Almost half, or 43%, of libraries offer free museum passes, according to 2017 data from library service company EBSCO. As a member of the Brooklyn Public Library, for example, you can get free passes to many institutions, including the American Museum of Natural History, where admission is regularly $23 for adults and $13 for kids ages 2 to 12. If you're a member of the Chicago Public Library, you can go to the Shedd Aquarium for free.

If you're a Costco, Sam's Club, or BJ's member, you can take advantage of other well-priced services and products aside from items you can buy in bulk.

For example, eye exams typically cost less in store than you'd pay at an eye doctor's office. Nationwide, the average price of an eye exam is a little more than $100, according to Angie's List. At warehouse stores, the price hovers around $70. For instance, in Southlake, Texas, an eye exam at Costco is $65. At a Sam's Club in Columbia, Missouri, you'll pay $59.

Generic prescription drugs are also often cheaper at warehouse clubs, McGrath says. "Use your Prescription Drug Savings Card to save when you fill your prescription at Costco's pharmacy," she says. "The program also offers free delivery to your home."

By capitalizing on the membership card you already have, you can easily shave dollars off your weekly spending.

The article Unexpected Discounts You Can Get From Costco and Other Memberships You May Already Have originally appeared on Grow by Acorns + CNBC.