The only person you can trust is yourself. Some rental car companies have been known to charge their consumers unnecessarily. For example, always double check that the mileage on the car matches the mileage on your rental agreement because if for some reason your particular rental agreement does not have unlimited mileage the rental car company could come back and charge you for the extra miles. This means that even if the rental car person tells you that you have unlimited mileage, unless you read all the small fine print in your rental agreement you may still be getting duped.
Moreover, when you drop off the rental when you return the rental to the car rental company make sure you sign the return agreement paperwork to make sure the rental company cannot come back and say someone else dropped off the rental car and the rental when returned had been damaged. If you are the person with the name on the rental agreement make sure if someone else drops off the car that they note on the rental agreement that they are responsible for dropping off the car for you and make sure that person gets a signature from the car rental agent at the drop off point signifying there is no damage on the rental car being returned.
Of course, always keep all your rental agreement paperwork since you never know what you may get surprised with at a later date. Always go over all the charges of your rental car agreement when you accept the car because one of the oldest tricks in the book is charging you for the costlier extra added insurance that you verbally declined when renting the car only to find the extra added insurance charges being added to your car rental agreement without you knowing about it.
SUPPLEMENTAL SOURCE: AOL AUTOS STAFF 9/24/13