Check all taxes and fees. Car-rental agreements might include extra costs such as an airport-concession fee, excise tax (the costs associated with registering a vehicle) and, of course, sales tax. Before you make your reservation, get a firm bottom-line quote that includes all extra charges.
Extra charges. You'll be extra charged if you return the car late. The time starts from the moment you take the keys. If you are after your scheduled return time, you could be charged for a full extra day. For some companies the grace period is only 30 minutes. Customer might have to pay additional charge for renting a car in one location and returning it in another.
Check branches. It's often cheaper to rent from a branch office that isn't at the airport. Ask your hotel if there's one nearby. Or type the hotel's street address into the car-rental company's Web site to find branch offices. Some rental companies, such as Enterprise, will pick you up and drop you off usually within a specified mile radius at no charge.
Inspect your car before departure. Make sure that the rental representative sees every significant nick, scratch, or dent on the vehicle and notes them on your rental agreement. Otherwise you could be held liable for damage that was caused by a previous customer.
Extra equipment. Some rent-a-car companies provide extras such as: ski trunk, child car seat, road map, tyre chains, etc. Check if they are in the car or you might be responsible for their absence.
Check Fuel. If you don't fill the tank before returning the car, you could pay dearly - two to three times more than at the pump - for the company to do it. As you are driving away from the rental-car lot, jot down the locations of nearby gas stations so you'll know where to refuel just before you return the vehicle.
Company contacts Keep company contacts you might need to reach them in case of accidents.