The First Tip – Read Your Rental Agreement before you leave and make sure you know what you have agreed to pay for. Many car rental agreements have hidden additional charges ie GPS Unit rental charges, or second drivers, so a quick read can save you extra charges upon your return of the rental car. Tip Number Two – Make Sure You Know What Your Insurance Coverage Is before you leave home., Call your insurance company and check with your credit card so that you know whats covered and avoid paying unnecessary additional insurance coverage. And Our Final Tip – Gas, Gas and More Gas! Always fill up your car rental before returning it to the rental station as most car rental companies charge up to four times the going rate for gas.