I don't have many rules except to please treat my car with love.
*Absolutely no smoking in the car* and be sure to return it with the same amount of gas you borrowed it with. Please follow the standard practice of returning the car as clean as you received it. There's an inexpensive car wash just around the corner from my place at 3193 Dundas Street West.
Dogs and cats are cool, but please return the car free of animal hair and/or lay down a blanket where the animal is sitting.