Even a lot of the so-called clean rooms that are really borderline dirty rooms.
In dirty rooms, its no-holds-barred. You'll see people trying to wreck the 15th place guy just as much as the 1st place guy. You can't expect to pass a car without them wrecking you. Some might call this fun, I just think it's stupid. I used to go into the rooms just to break in some of my stock cars, but I couldn't stand the whiny kids in there; most of which acted like they just discovered the "Book of Profanity" and were over-eager to spread its teachings.
A clean room to me follows these guidelines:
Everyone stays in pit lane until race starts.
It seems that a lot of black screen issues are caused by people driving around the track before the race starts. In most NASCAR clean rooms, everyone knows to stay in the pits. People who don't are usually met with the boot.
Drivers give other drivers space
I see this happen way too often. After the race starts, the cars in front have nobody to draft up to, so they accelerate slower than everyone behind them. Then, the people at the back of the pack have a huge run of speed from the draft, and hammer into the lead 3 or 4 cars, causing a pile-up before anyone exits the first turn. Good racers know that if they've got a run going, but have nowhere to go, they'll back off the throttle and give that person space until things spread out a bit. Same goes for trying to make a hole where one does not exist. Almost the same as above, people have a huge run of speed at the end of the straightaway at Daytona, pile it into the corner, onto the apron, or just into a pack of cars, and cause a huge wreck. Drive intelligent, make your passes when you have the opportunity. Driving like its the last lap on the first lap is a recipe for disaster.
No passing below the yellow line, unless forced under it
Pretty clear rule from my point of view. The yellow line at Daytona is there for a reason. I see to many people driving down on the apron, losing control, drifting up and taking out a pack of cars. You've got the low line and the high line, pick one. The grass and the apron are not places to pass. Also, on the last lap coming to the finish, don't try and wreck people because they are about to pass you. I can't tell how many times I've had a draft run on the leader coming to the checkers, and the leader will sideswipe me into the wall just as I am about to pass him. Sure, it gets you the win, it also makes you a talentless, sour, reckless douche of a driver who couldn't win fair-and-square. If someone has a run on me at the finish, I'll hold the yellow line. I don't block, swerve up, or intentionally try to take the person out.
Don't ever, under any circumstances, in any event, any time, or any place DRIVE BACKWARDS!
I swear to God, there should be a special place in gaming hell for people who do this. They are usually people who don't ever run Nascar races, come into the room, spin themselves out, then think it funny to drive backwards and ruin the race for everyone else. It's bad when the race is only 5 laps, even worse when your twenty minutes in to a 50-lapper, and you get taken out by some childish moron with a bad attitude. Driving backwards in a clean room equals and instant boot if I'm hosting. And I've actually had people try to justify why they went backwards ("he spun me out, so I wanted to get back at him"). People like that have no place in clean rooms.
Other than that, just be polite and courteous. If you accidentally spin somebody else, apologize. **** happens. I'm more likely to let it go if the person says, "Hey man, sorry about that, was trying to give you a boost and got a little loose." That to me shows respect for other racers. Compare that to the idiots who spin people out, then when called on it, usually deny and fire back that it is you that is driving terribly. You get enough people boiling over about **** that happened in the last race, eventually you're going to have a room full of headhunters looking to get some revenge. It's a really easy way for a clean room to turn dirty real fast.
And if you've got a microphone, use it. So many crashes could be avoided by letting people know where you are and if you're about to pass that person. "Coming low, Racer1234!", or "On your highside, Speed4321!". Keeps cars from coming down on cars trying to pass and causing huge wrecks.
But it is really hard to find good clean rooms. And they don't last very long from my experience. All it takes in one bad apple to come in and ruin it for everyone. Sadly, they outnumber the clean, respectable drivers by a large number.