Don’t stick your limbs out of windows.
Don’t stick other people’s limbs out of windows.
Don’t shout "brake, Brake, BRAKE!
Don’t shout “brake, Brake, BRAKE!” when I’m pulling into a parking spot.
You gasp and clutch your heart one more time, Mom, and I swear to god.
Anyone is free to have input into the musical choices as long as they don’t have a stick up their ass about it.
That reminds me of another one my husband and I have - any sightings of things that might run in front of the car must be accompanied with pointing. Not once but twice in his life, he was the passenger in a car and saw some deer that could have run out in front of the car, and told the driver, and the driver thought he was talking about the deer on the driver’s side of the car and didn’t realize he was looking at deer on his side of the car. Hence the rule. 
Oh, I have another rule.
Cows On My Side starts the minute the car leaves the driveway regardless of the duration of the trip and the odds of actually driving by cows. And the passenger side people better play nice or I’ll purposefully change the route to drive by a cemetery on their side.
My rule is…if you see something dangerous or scary, sing out! I like “back seat drivers.” I want to be told, “Watch out for that truck!” I’d a million times rather someone give me a scare and it turn out to be nothing…than that I miss seeing that truck and get killed by it!
I always tell this to my passengers, especially on long trips. If you are at all in doubt about whether or not to say something…say something!
Mine’s a dog truck too, so the only rules are no smoking and must wear seat belts.
For me, the radio thing isn’t just to make sure I hear music that I like, it’s because having the passenger futzing around with it is distracting to me. With their hand/arm in my peripheral view, it’s hard not to glance over to see what they’re doing. Plus, the whole business of “how do you get the CD out?” and “What are the station presets?” and “how do you hook up the MP3?” Just don’t. I’ll make sure there’s something we can both agree on, but leave it alone.
A long journey would probably be an exception, as the learning time would be made up for, but just around town, leave it alone.
No smoking, and snacking on something non-messy like Twizzlers is fine. I hesitate about drinks. They’re a lot harder to clean up. Non-sugared or milked, with a lid and a straw, maybe, depending on who my passenger is. I’m surprised the “no food” people are allowing lattes in the car…
Rules for the car!?!?!? HAAAAAHAAAAAhahahahahahahahahahaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!!!
If I made them, they would just break them.
Gas, grass, or ass.
Nobody rides for free.
Im honestly surprised nobody said it first.
Really though, driver drives, stay out of my mirrors, seatbelt on.
Seatbelts at all times, do not unbuckle until the car has STOPPED (my daughter is bad about this - she’ll unbuckle as we’re pulling into a parking space).
I would not let someone smoke in the car, though the topic has never come up.
“Tricky driving”: evolved from when the kids would suddenly shout out frantic questions as we were driving. This can be… startling. That can be… bad, if you’re going through one of the hellish interchanges on the beltway. So we started the habit of asking the kids to be quiet until we told them they could talk again, just before we got to such an interchange; once we were through it, we’d tell them they could talk again. That got abbreviated to “Tricky Driving”.
To Mama Zappa:
I’m gonna be laffin’ for the rest of the day! Your request to have “no tricky questions” while stuck in rush hour traffic re-awakened old memories.
I was on one of the “fly-over” ramps, which has a notorious merge with a very busy freeway. Right in the MIDDLE of traffic, a voice pops up from the back seat: “Mom, where do babies come from?”
Oh, yeah.
~VOW
If a passenger yells at a bicyclist (“Get off the road!”) they stop being a passenger and become a pedestrian at the closest safe place to stop. A former co-worker seemed to think this was unreasonable.
Oh, yes! I forgot my most important car rule (because it rarely comes into play with the people who ride in my car): You are not *ever *allowed to make obscene gestures, yell, or otherwise antagonize other drivers, pedestrians, bicyclists, etc. There are too many crazies on the road, and I have no desire to be the star of somebody’s road-rage incident because my passenger can’t keep him- or herself under control.
You people actually let passengers ride in your cars?
Well, it turns out that it’s illegal to make them cling to the roof or bumpers, so yeah.
No spaghetti with or without meatballs shall ever be eaten in the car.
Lunch break, “Whose going with who?”
Me, “Smokers, come with me!”
That said, my only real rule is that passengers must wear seat belts. I turn the radio down to a dull hum, and I will turn it off if requested, but I guess my other rule is that I won’t change the station.
I thought that was a library book rule. 
I only routinely drove with other people (besides my gf) when I went to a different college and drove people back to the apartment complex several of us lived in. I had only one rule:
If you open the window to whistle at, hit on, or otherwise heckle chicks, you’re walking home. It’s annoying, it’s rude, I don’t want to be associated with it or enable it. The only exception is if you know the person and are playing a joke.
Note that I have no problem with hitting on people, but cat calls from cars aren’t “hitting on,” they’re not going to get you a date, or really anything other than someone whose day just got worse +/- a middle finger. I made this rule since I’ve had plenty of female friends, and when guys drove by and did that to them when I was there it was the most disruptive, annoying thing ever.
Other than that, food, drink? Fine, whatever, try not to spill. I guess I usually control the music, but that’s not really a rule.
Yeah, I spent a fun hour driving on Malaysian B roads in the countryside. Unfamiliar, poor road markings, no street lights. Senior uncle (as in, he who must be respected) in the front, 3 adults and a kid in the back.
Maintain a conversation with him the whole way. Then my wife wondered why I was sweating when we reached the uncle’s house.
No smoking.
No screaming. This really only applied when the oldest was about two and thought it was funny to scream at random intervals from the back seat.
If there’s more than one kid in the car, they all ride in the back. I’m not dealing with whose turn it is to ride in the front seat.
Other than that, I control the radio, but I’ll compromise most of the time. Not always, because I like to torture kids, you know.
These days it doesn’t matter much, since I almost never have passengers.