Renting a car? Know whether your card adds insurance

You're standing at the car rental counter, anxious to get on your way, but first you have to deal with the representative who's pushing you to sign up for the agency's car rental insurance ''just in case.'' Should you? Most Americans have no idea what to do when offered collision damage waiver (CDW), the expensive add-on coverage offered -- often forcefully -- by rental car agents. Given the tricky exclusions listed in the fine print of most credit card policies, chances are, they're even more confused about what their credit cards cover.