1) Do NOT rent at an airport location.
2) Sometimes pays to join a frequent renters program such as through Enterprise.
3) Do NOT let them fill the gas tank at the end. Bring the car back fueled up.
4) Check with your own car insurance company (if you have one) as to whether they will cover you during a rental. That way you may be able to escape the various insurance charges from the car rental company which are pretty high.
5) Some credit cards provide car rental insurance coverage.
https://www.cnbc.com/select/credit-card-car-rental-insurance-how-it-works-cards-that-have-it/
6) Also, when you first get the car, make sure the license plate and/or registration is current (not expired). And make sure that the registration is there (eg in the glove comparement, NOT missing).
7) Have them print out the rental agreement to carry with you, as opposed to “we’ll e-mail it to your phone”.
8) Make sure to check for damage at the start AND end of the rental. Also write down the starting and ending mileage.
