If you tailgate someone, and they have to stop suddenly, you will likely crash into them. I love Canada, but the drivers up there drive less than a car length apart at 120kph and traffic will suddenly stop for no apparent reason. They apparently have the skills down pat, but its not an enjoyable experience. Driving on someone's ass so nobody can cut in front of you is just asking for trouble.
If there is a line of traffic because of merging lanes ahead, speeding up the side instead of waiting your turn makes EVERYONE behind you wait longer. If you do this, you apparently never learned in kindergarten that cutting in line is not cool. Take a time out.
This rule also holds true for people passing on the right. I'm fairly certain its illegal in most states. Take a time out and $100 fine.
Slow people in the fast lane are also rude in some cases. Even if you are going the speed limit, you should at least check your rear-view periodically. Most people don't drive the speed limit. Even the police accept some leeway on speed limits in most cases. Getting back over when you can generally aids in the lessening of tailgating problems, and "forcing" people to pass on the right.
If you are turning, or changing lanes, use your turn signal. That's what its there for. If you do it enough, it'll become habitual. Kinda like putting the toilet seat down for the ladies. Its nice and doesn't take much effort.
If you are at a stoplight on a two lane road, and the guy opposing you at the light is turning left, let him turn left, particularly if there is a line of traffic behind him. If traffic is going slow, let someone turn or merge in. It'll make them feel good and won't really slow you down noticeably. Think of it like spreading a smile.
If you must take your aggressions out while driving, don't take it out on other drivers. You don't even know them. They are not out to get you, but if you piss off enough people, they might be. You do have a license plate number, after all.
Retaliation is always a bad move. If someone cuts you off, don't go out of your way to try to cut them off. Either they did it accidentally, or you'd be stooping to their level of filth, and threatening to cause a real accident.
If everyone followed these rules, the road would be much more pleasant to drive on. Feel free to send me your complaints to add to the list.