4. Think twice about insurance.

When renting a car, you'll be offered a collision damage waiver (CDW) and a loss damage waiver (LDW). The first covers you in the event of a collision, while the second covers any loss to the rental company. Both kinds of coverage are a good idea, but not if they duplicate coverage already included in your own insurance policy. Most insurance policies offer liability coverage to protect you if you injure someone in an accident; some also cover rental-car damage via comprehensive and collision coverage. Check your policy or call your insurance agent to verify coverage before signing up for a vehicle. If you're renting the car with a credit card, your card provider may pay for vehicle damages associated with an accident. Check with your card company ahead of time to make sure.

There's one caveat. The collision damage waiver covers "loss of use," the charge levied by the rental car company to cover its lost income when the vehicle is out of service. In most states, auto insurance policies don't cover this loss, so if you have an accident, you may wind up having to pay this charge out of your own pocket. As such, getting the collision damage waiver may be a good idea.

5. Book early.

It's not just a clich ; the early bird really does get the worm, and he usually gets it much cheaper than everyone else. Rates depend on how many vehicles the company has on the lot at the time the rental is made, so sooner is better. Reserve your car at least a week in advance.

6. Think twice about prepaid gas.

Typically, renters have two choices when it comes to fuel: You can pay for a full tank of gas in advance and bring the vehicle back empty (or less than full), or you can opt to refuel it yourself just before returning it. Rental car companies suggest that paying in advance will add convenience and that the low rates offered will save you money. Well, they're right on the first part but wrong on the second. Paying in advance is an added convenience; if you want to save yourself the hassle of a trip to the gas station or avoid a last-minute rush when you're trying to make a plane, pay away. But unless you plan on using the entire tank of gas, prepaying will cause you to pay for more fuel than you've actually consumed. From a financial standpoint, prepaying is a bad idea unless you're absolutely certain that you'll use the full tank.

7. Be careful of upgrades to larger vehicles.

Sometimes, rental car companies will offer free upgrades to larger vehicles. They do this mainly because compacts tend to be in high demand. This sort of upgrade may seem like a great deal for you, the renter. If having a larger vehicle will genuinely enhance your rental experience, then take the upgrade. But if you have no real need for the extra space, it's cheaper to decline. Larger vehicles burn more gas, so that "free" upgrade isn't really free you'll wind up paying for it at the pump.

8. Steer clear of airport pickups.

Picking up a rental car at the airport can be more expensive due to taxes and fees. Try looking at nearby neighborhood locations to save money. A recent Travelocity study showed that renting at an airport costs more than 11.5 percent more on average than renting at a neighborhood location. Texas airports were the chief offenders, but airports in states like Arizona, Ohio, Maryland, Missouri and New Mexico also cost renters more in taxes and fees.

9. Got kids? Seat 'em yourself.

If you're traveling with a little one, you can save yourself some coin by bringing your own child safety seat. One rental company we surveyed charged almost $10 per day for child safety seat rental. Obviously, this can tack a significant amount onto your car rental expenses, so if you're able to, bring your own child safety seat. If you're renting a minivan, though, know that some rental minivans include integrated child safety seats at no extra cost.

10. Join the club.

Many of the larger companies offer club membership in which members pay a yearly fee in exchange for certain perks and privileges. These clubs can save you money with benefits like free rental days and airline miles, but you'll likely only see savings if you're a frequent renter. If you fall into this category and use rental vehicles more than occasionally, go clubbing.