I have one to add that has been driving me nuts ever since I moved back to my hometown and travel with my sister more often:
To adjust the temperature in her car, my she keeps the temperature setting on the coldest possible setting and adjusts the fan speed when she is too hot or too cold.
I don't know how many times I have told her that if she sets it to the desired temperature JUST LIKE HER HOUSE then she would rarely have to touch it. She doesn't get it and refuses to try it. Her car has dual zone heating/ac in the front, but it is absolutely pointless to use when she is adjusting the fan speed.
