Keeping Intersections Clear / Special Stop Sign Rules

Caveat: I don't know the traffic laws of any country except the United States, so I don't know how or if the following applies anywhere else.

It's remarkable both how often I see this written on the street or on signs, and how often I see people fail to do so. When stopping at an intersection, a long enough line of cars will often extend past another intersection. Traffic can also cause this phenomenon. Don't go into an intersection unless there is room for you on the other side. There are a number of reasons for doing this. For instance, if there is a stoplight, you will probably still be stuck in the intersection when your light becomes red, and everyone else will have to wait for you to get out of their way.

If you are at an intersection like this:

Pardon the quality; I made it myself

and you are the red car, it is technically your right of way. However, if the traffic is moving slowly and the blue car would never have a chance to get in while following the standard rules, it is polite to stay out of the intersection and allow the blue car to advance (they may move forward on their own, but wave them if they don't). The cars should continue to advance as if merging; one car from the left, then one from the right, etc. Usually, traffic planners design intersections to avoid this problem, usually replacing the stop with a light, but often things like big events will cause unpredictable traffic problems.