So you think you're covered. Damage, theft, personal effects - hey, you've even worked with your insurance agent to make sure you're covered in case of liability. Good for you. And yet, too many people who think they've done the responsible thing end up surprised when, after an accident, their insurance company won't foot the bill for something the rental car companies call "loss-of-use".

Loss-of-use is a fee imposed by the rental car company on the customer to cover its lost income while the vehicle is out of commission from an accident--even when the accident may not have been the customer's fault.

Loss-of-use, along with various "administrative fees" imposed by the rental car companies, usually come as a huge surprise to unsuspecting renters. These charges can quickly add up. While buying the Loss Damage Waiver (LDW) or Collision Damage Waiver (CDW) sold by rental car companies means you're off the hook completely in case of mishaps, it may not be the most cost effective solution. There are ways to bulk up your personal coverage. This way, you won't have to overspend when you pick up your next rental car. Here's a checklist:

1) IS YOUR STATE ON YOUR SIDE?

Never assume your personal auto insurance policy covers you for anything when you rent a car. Always read it over. Even if it sounds like you're free and clear, remember this: Many policies don't address loss of use issues when you rent.

In some states, lose of use coverage is automatically covered by a renter's personal auto policy. These states are: Alaska, Connecticut, Louisiana, Minnesota, New York, North Dakota, Rhode Island and Texas.

Make sure you know before you refuse the insurance offered at the counter.

2) BUT WHAT ABOUT MY CREDIT CARD?

Yes and no. Yes, some cards that insure you when you rent a car have you covered. Others do not. If you hold a standard card and rent cars frequently, that card should be a Visa. The latest fine print states that you are covered not only for collision and damage, but also towing and "valid" administrative and loss-of-use charges. What's valid? Rentals under fifteen days in your home country, or thirty-one days outside your home country. You need to use the card for the entire transaction, as well. (No swiping with one and paying with another.) Additionally, Visa explicitly states that it uses fleet utilization logs (documents that show the company's business truly suffered as a result of your accident) to help sort the claim. Be warned - some companies jealously guard these logs and sorting out responsibility can often take time.

MasterCard holders should look very closely at their policies; the brand's "MasterRental" coverage that comes with your card does offer loss-of-use coverage for charges that are "reasonable and customary." There are, however, plenty of qualifiers and exclusions in the fine print of the coverage document - again, read it. Also note that like most credit card insurance policies, this coverage is secondary to your existing auto insurance.

American Express holders should seriously consider subscribing to the company's Premium Car Rental Protection package. Standard cardholders are sometimes alarmed to learn that the automatic coverage can be a bit scanty. We're big fans of the aforementioned premium plan offered by American Express. This policy, a bargain at $24.95 for the rental period (some time restrictions apply), explicitly states that it will cover you in case of loss-of-use, with stipulations that are similar to Visa's. Make sure to read the paperwork they'll send you when you sign up.

Bottom line: Some credit card policies have your back. Others do not. Know which one is in your wallet.

3) DON'T GIVE IN AT THE COUNTER

It happens time and time again -- agents will often successfully prod customers into buying the insurance that's offered over the counter. Don't be surprised; as companies struggle to find ways to bring in new revenue, the pressure is on agents to sell. If you've read your policy and it says you're covered, don't give in. If you haven't, our best advice is to buy the over-the-counter coverage, suck it up and, for the love of God, be prepared the next time.