Cost-conscious travelers, whether on the road for business or pleasure, know that one place to shave trip-related expenses is at the rental car counter.

Michael Taylor, senior director of travel services for J.D. Power and Associates, a global marketing information and services firm, says people are looking closely at their rental car bills and shopping around more.

In many cases, these careful consumers discover rental car agents are eager to play “Let’s Make a Deal.”

But if you want to drive off with a real bargain, you need to know the rules of the renting game. These dozen tips will help you get the best deal.

1. Shop the Internet

Internet sites sometimes have better deals because they are cheaper for the company to operate, says Jack Gillis, public affairs director for the Consumer Federation of America, a nonprofit advocacy group.

Look at multiple independent travel sites (three popular ones are Travelocity, Expedia and Orbitz) and then review three car rental Web pages, says Gillis, author of “The Car Book.” Because of special arrangements, says Gillis, you’ll often find that one of the travel or car company sites will have a better deal.

2. Ask about discounts

Frequent-flier programs, credit cards, hotels, national clubs and some companies and government agencies have negotiated discounts. Two popular groups that regularly offer membership breaks for renters are AARP and AAA. To be sure you don’t miss out on anything, Gillis says to always ask what discount plans are available.

3. Time your reservation

Everything’s a trade off. By reserving early, you lock in your car and your rate. But if you rent your car before you book your airline or hotel, you might miss out on a reciprocal deal. So do a little research and ask a few questions before you book.

That said, several industry experts recommend booking your car as soon as possible. “It’s unlikely you’ll get burned [on rates],” says Justin McNaull, spokesman for AAA. “But if you wait, there is a significant chance you will not get the same choice of cars.”

If you want to book during peak periods, such as long holiday weekends, reserve six weeks ahead or you’ll be blocked out, says Neil Abrams, president of Abrams Consulting Group Inc., a consulting and market research firm specializing the auto rental and fleet industry. At other times of the year, the lead time varies with the company, he says. “I would say a couple of weeks is fine.”

4. Consider how long you need the car

Although you need the car for only two days, you might get a better price if you rent it for longer. “Don’t be afraid to look at a weekly rate,” says McNaull. “It’s sometimes cheaper than a four- or five-day rental.”

Online renters should play with the date pairs and see if that extra day will net a better rate, he says, adding that sometimes travelers have to hook into a weekend or weekday to get “the deal.”

5. Look beyond the big guys

Be willing to investigate lesser-known agencies, says Abrams. “There are many secondary brands that deliver a quality car at a competitive rate that are not necessarily household names.”

And if you like the staff or cars at one agency and the prices at another, ask your preferred agent to match a competitor’s price. The worst that can happen is a “no” and you lose nothing.

6. Compare non-airport rates.

“In general, prices have gotten more expensive at airports,” says Taylor. A recent J.D. Power survey found that airport access fees, the surcharge leasing companies pay to operate out of the airport, are usually passed along to consumers.

If you do find it cheaper to rent away from the terminal, don’t forget to factor in the cost of getting to and from the offsite agency. If there’s no shuttle and you have to grab a cab, it might be cheaper to pay the higher fee.

Also make sure that the away-from-the-airport agency will be open when you want to return the car. A bargain’s no bargain if you’re standing in front of a closed office on Sunday morning with a car you can’t return and a plane that leaves in two hours.

7. Shop the counters

If you show up at an airport without a rental reservation don’t be afraid to go counter to counter comparing deals. “You’ll be amazed,” says Gillis. “The difference can be up to 50 percent at the same location.”

8. Think about where and when you want to return the car

If you want to leave your car in a place other than where you rented it, you need to include drop-off charges in your shopping, says Gillis. It some cases a higher daily rate that offers lower drop-off fees might be cheaper.

9. Book ahead if you have a special request

Need a child safety seat or a ski rack? Reserve it at the same time you reserve your car, says Gillis. Ask about extra charges and get it in writing.

10. Ask about mileage

Some companies include unlimited miles as long as you stay within a certain region. Others cap the mileage. Estimate your needs and shop around.

11. Consider gas and insurance

These two items can add to the cost of your rental car.

Unless you know you’re going to be scrambling when you drop off the car, offer to fill the tank yourself. Otherwise, it’s usually a pretty pricey fill-up at the rental office’s pump and you can’t take any left over with you, says McNaull.

As for insurance, talk to your own agent first. “Be sure you know what your own auto coverages are regarding renting a vehicle,” says Abrams. Most customers don’t know or understand the rental coverage offered at the counter or how their own insurance will treat a rental car.

12. Never stop bargain shopping

Haggling doesn’t end just because you’re at the rental counter, reservation in hand. Gillis recommends you ask if the company will give you any free extras or upgrades. He estimates your chances of getting one are about 25 percent. That’s well worth it, he says, “for the three seconds it takes to ask the question.”

When McNaull was renting a car in Orlando, the company offered to upgrade him from a midsize to a Jaguar for $12 a day. He declined only because he was traveling on his corporate credit card. “There would have been too much explaining,” he says with a laugh.

“Rental car companies want to make money,” says McNaull. “But they also want you to be happy so you’ll come back. And if you discover the person in front of you is paying 20 to 30 percent less, that doesn’t leave you a happy customer.”