Please no animals in the front seats (not even small dogs). Dogs on the covered rear seats or the trunk area are ok.
No smoking anything in the car at all. Any remaining odors will be assessed a fee up to $500. That includes odors from marijuana, cigarettes, cigars, incense, pet/human waste, rotten food, exploded cologne/perfumes, etc. Just don't spray, spill, or smoke anything in the car and you should be alright.
Return the car how you received it. There will be a minimum cleaning charge of $50 if post-trip cleaning isn't selected and the car is returned dirty. Take advantage of the free carwashes during your trip, however there is no fee for returning the car unwashed so if you don't have the time to wash it, don't worry about it.