Ok navigation. Hills to the left and you are going south. Hills to the right and you are going north.
Altitude. Help with the shopping.
Car Cleanness. Seriously with this one. Even in this weather the car has to be cleaned before you start work. Pet hate of mine is people who don't wash their cars when it's raining.
Car smell. Check something like fruit hasn't been left in the car you haven't noticed?
Level of service. You are giving cheap rides to entitled Millinials sorry they're never going to appreciate you.
Conversation. Right wing political views will create problems as will left wing views. Mostly right wing though. Or left wing.
Religious views are a problem.
Off jokes or any jokes for that matter can offend.
Sometimes people are just a pain in the backside and you get a run of them..
Keep the car clean be nice and don't talk too much.