As consumers try to keep up with the fast-shifting world of credit cards, looking for ways to sidestep new fees or avoid rate hikes, they may be missing out on savings from benefits they already have.

Even as card issuers continue to clamp down on credit limits and rewards programs, they ve left intact a variety of perks that, when properly used, can save consumers hundreds of dollars.

Free benefits like extended warranty protection, lost-luggage reimbursement or purchase protection aren t nearly as widely-advertised as 0% introductory interest rates or the ability to earn bonus rewards points, yet they are a staple with any credit card that has the Visa (V) or MasterCard (MA) logo, or is issued by American Express (AXP) .

These perks, also known as fringe benefits, are typically provided by Visa, MasterCard and American Express and paid for through interchange fees (paid by merchants for each credit-card transaction), says Adil Moussa, an analyst with market research firm Aite Group.

Yet fewer than 15% of credit-card holders use these benefits, according to Robert McKinley, the founder of CardWeb.com, which provides industry research and analysis.

That shouldn t come as a surprise, as these benefits are typically described in the tiny-print booklets that consumers receive with their credit card and hardly bother to read, says Odysseas Papadimitriou, the chief executive officer of Evolution Finance and credit-card portal CardHub.com. It s really unfortunate, because they are really good benefits, he says.

That s not to say that taking advantage of those features is easy: There is typically a lot of paperwork involved and, because these benefits are so rarely used, you may have to work with customer service reps who aren t aware of how they work, Papadimitriou says. But jumping through hoops may well save you hundreds or in some cases thousands of dollars.

Below, the details on six credit-card benefits and how to qualify:

1. Auto rental collision damage waiver

What it does: Reimburses you for the deductible portion of your personal auto insurance policy (or all covered damages or theft, if you do not have auto insurance), as well as administrative and loss-of-use damages imposed by the car rental company and reasonable towing charges.

The catch: Does not apply if you rent a car for more than 15 consecutive days in the U.S. or 21 consecutive days abroad. The loss or theft of your personal belongings and personal liability charges are not covered. And don t forget to decline the collision damage waiver (CDW) or loss damage waiver (LDW) option offered by the rental company.

Value: $10-$12 to $18-$20 a day. That s how much you would pay if you purchased a collision damage waiver from the car-rental company, depending on your location, the type of vehicle you rent and which rental company you use, says Neil Abrams, an auto rental consultant in Purchase, N.Y.

2. Extended warranty

What it does: Doubles the free-repair period of an item s original manufacturer s repair warranty, up to one additional year. Typically includes purchases made outside the U.S., as long as the item has a valid original manufacturer s U.S. repair warranty, store-purchased dealer warranty or assembler warranty.

The catch: A wide range of items aren t covered. Those may include boats, cars, aircraft and any other motorized vehicles and their accessories; items purchased for resale or professional use; real estate and items intended to become part of real estate (for example, garage doors and ceiling fans); computer software; medical equipment and used, antique or collectible items.

Value: $15 to $270. A two-year Geek Squad Black Protection Plan from Best Buy costs anywhere from $29.99 to $539.99, depending on the type of item you purchase and its cost. (Keep in mind, your credit-card company does not have its own team of service support geeks. Its coverage will simply extend the terms of the warranty you have from the manufacturer.)

What it does: If something you bought with your credit card is damaged or stolen within 90 days, you can receive a refund of the purchase price.

The catch: This protection has many exclusions, including items that are lost without any evidence of a wrongful act or are stolen because of a lack of due diligence. Used, antique or collectible items are not covered.

Value: Refunds limited to $300 (American Express), $500 (VISA) or $1,000 (MasterCard) per item. American Express has an additional program with refunds of up to $1,000 on certain types of items, including clothing and electronic equipment. Caps on the total refunds received by card holders also apply (e.g., a total of $25,000 per cardholder with MasterCard or $50,000 annually with American Express).

4. Lost luggage reimbursement

What it does: Reimburses you for the cost of luggage (and its contents) that has been lost or damaged by a common carrier (plane, train, helicopter, ship or bus).

The catch: Restrictions or limitations vary based on the card issuer or payment network. Visa and MasterCard generally will pay the difference of the amount claimed and any payment by the common carrier, up to $3,000 per trip ($2,000 per bag for New York residents). Both companies encourage card holders to contact their financial institution to confirm specific coverage levels. American Express pays up to $1,250 for carry-on baggage and up to $500 for checked baggage. (AmEx Platinum and Centurion members receive up to a combined $3,000.)

Value: Up to $180. You can purchase additional coverage for lost luggage from the airline, typically at $6 per $100 of value.

5. Roadside assistance

What it does: If your car breaks down on the road (and you are generally at least 50 miles away from home), your credit-card company will send someone to the rescue.

The catch: You will still be charged for any services received (e.g., towing, jump-starts, gas delivery or tire changes.) Visa and MasterCard say you can still end up saving money, because the fees for these services are pre-negotiated. (If you are driving a rental vehicle, make sure to check whether you can be reimbursed for these costs under the card s auto rental collision damage waiver.)

Value: $38 to $80 a year, the cost of individual AAA membership, depending on the location. (Keep in mind that the cost of road services is included in AAA membership, so that may be more cost-effective if you expect to use such services often.)

6. Concierge

What it does: Available with the Platinum Card from American Express, as well as the premium levels of Visa and MasterCard (Visa Signature, MasterCard World and MasterCard World Elite), concierge services can help you book travel, make restaurant reservations, get tickets to concerts or sporting events, pick out gifts (including hard-to-find items) or plan a party.

The catch: You will pay the cost of all services or items received, so if you are a type-A shopper or on a tight budget, you re better off doing your own research. In addition, many premium credit cards that offer this service have annual fees, so they're not entirely free. For example, the AmEx Platinum card will set you back $450 a year.

Value: $25 to $55 per hour. The hourly rate charged by concierge services varies, depending on your location, says Katharine Giovanni, chairman of The International Concierge and Errand Association, an industry group. Todd Wheeler, the owner of Denver-based Concierge Resources, says prices also vary depending on the type of services performed: Expect to pay more for planning an around-the-world trip than, say, picking up your dry cleaning.