If you frequently rent cars when you travel, you already know this expense is highly variable.

The price for your rental can surge astronomically from day to day and even week to week. It can also depend on the rental company, where they’re located and how busy they are during your rental period.

It’s best to be proactive. Depending on where you rent a car and who you rent it from, the prices can rise and fall frequently. The best thing you can do is compare as many options as you can, check around for pricing every few weeks, and book refundable car rentals so you can cancel if you find a better deal.

If you’re hoping to save money, it can all be a little stressful. Here are some of the best ways to ensure you’re getting the best deal you can find:

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Shop Around

Since prices vary so much between car rental agencies and discount vendors, one of the best steps you can take is just shopping around. Search all the popular discount sites like Expedia and Priceline for their rates, or use a service like Kayak.com to compare rates from several different websites at once.

You can also shop for rentals on Costco Travel, which is notorious for offering some of the best rates in the business.

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Book Early, Then Rebook

Another great way to save money on car rentals is booking refundable rentals and rebooking when prices drop. This is the strategy I use to save and it works well.

Earlier this month, I booked a four-day rental in Switzerland for $380. After keeping an eye on prices, however, I rebooked the same car with the same rental agency through Expedia for just $204. With a month left before we leave, it’s pretty likely I’ll rebook again and cancel that booking, too.

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Use Autoslash

Autoslash.com promises to search for lower prices and rebook your car rental when rates drop. Basically, they take the work out of the equation and do the heavy lifting for you.

Add your rental to Autoslash.com to get started. From there, you’ll receive notifications if (and when) prices drop. Once they do, you can cancel your original booking and rebook at the lower price.

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Join a Rewards Program

If you find yourself renting cars from the same handful of companies over and over, you can benefit by joining their free loyalty programs.

With Hertz Gold Plus Rewards, for example, you can score a domestic, one-day weekend rental for less than 600 points. Avis, Enterprise and National all offer their own programs that reward your loyalty with free and discounted rentals.

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Get a Travel Credit Card

Certain rewards and travel credit cards make it easier to earn discounts with your favorite car rental agent. Hertz grants Citi cardmembers with a 5 percent-20 percent discounted rate, for example. Citi cardmembers can also enroll in Hertz Gold Plus Rewards for free.

The newer Chase Sapphire Reserve is another rewards card that offers discounts on rental cars. Just for being a cardholder, you qualify for discounts from leading rental agencies like Avis, National Car rental and Silvercar.

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(TravelPulse is a leading travel authority on the Web, providing consumer travel news and insider tips and advice for an ever-changing travel world. Read more stories at travelpulse.com.)

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