Fasten your seat belt: Car rental rates have hit overdrive. Even an econo-box can command $35 or more a day in the U.S., plus taxes and fees.

Scott Thompson, president and chief executive of Dollar Thrifty Automotive Group, expects current trends to continue in 2009.

To get a grip on your rental budget, try these seven strategies:

1. Leave the airport: Travelers pay dearly for convenience. Rental cars at airports, which typically have higher rates and a host of fees and taxes that aren't charged elsewhere, can cost three times as much as off-airport rentals.

"If you want to save," said industry expert Neil Abrams, president of Abrams Consulting Group in New York, "take a cab to where you're going and rent a car, unless the cab fare is $50," which is not unusual in big cities.

In San Francisco, an economy car I priced online from Enterprise Rent-a-Car for a three-day weekend cost about $164, including taxes and fees, at the city's airport but only $70 at Enterprise's downtown site.

To get those savings, take a half-hour BART train ride from the airport to the Powell Street station ($5.35) and walk about three blocks to Enterprise.

2. Avoid the extras: Waivers and insurance to cover collision damage, liability and loss of personal effects can cost $25 or more a day. You don't need this coverage because it's already provided by your auto, homeowner's or renter's policies.

3. Shop around: Rates vary among companies and outlets. Web sites such as Expedia, Travelocity, Orbitz and Breeze-Net make comparing easy.

4. Take a chance: A car is a car is a car, no matter whom you rent it from. So you don't give up much by bidding on Priceline.com or booking through Hotwire.com's "Hot Rates," where you learn which company you're renting from only after you reserve the car. And you can save a lot.

When I checked Hotwire, it charged half as much for the San Francisco airport rental as Enterprise. One downside is that these "opaque" bookings are usually nonrefundable.

5. Look in your wallet: AARP, AAA and Costco members and some credit-card holders, among others, might be entitled to discounts of 5 percent or more. Make sure to carry your card.

6. Follow the rules: Return your car on time or you might get dinged for late fees. Don't count on a grace period. With inventory tight, station managers are "much more keeping to the letter of the law," said Chris Brown, editor of Auto Rental News, a trade magazine based in Torrance, Calif.

7. Fill it up: Note the prices and locations of gas stations near your rental site so you can return your car with a full tank.