I have always believed in courteous driving. It is not just a matter of not offending anyone, but is also a way of improving traffic flow and, as a result, of getting there faster yourself.
Whenever I am out driving, especially when I am driving close to rush hour, I try to practice courteous driving. Sure, this includes letting buses pull out from their stops, but it also includes a lot of techniques on the highway. I always try to signal my lane changes and my turns a reasonable distance ahead. I prefer to be sure that the person in the next lane is aware that I am coming over before I appear in front of him. This is not just courtesy, but common sense; if he knows I am coming over, he is much less likely to hit me.
Of course, in exchange for the courtesy of signalling, I expect the courtesy of being reasonable about letting me change lanes. For my part, if someone signals that they wish to change into my lane, and I can reasonably do so, I make a point of making space to allow them to do so safely. After all, if they were already ahead of me, why should I mind them being ahead of me in my lane?
While I believe in courteous driving simply because it makes the drive more pleasant for everyone, I have come to realize that it also helps the traffic flow. Have you noticed that when someone cuts you off, you suddenly have to slow down, which also causes everyone behind you to slam on their brakes? I have often seen traffic jams which were caused this way, and, unfortunately, a few accidents. On the other hand, when somebody signals that they want to come over, you can slow gracefully, and the traffic behind you may not even be affected. At the least, you will not be contributing to a sudden slowdown, or a possible accident.
And by signalling your own lane changes you are giving people a chance to make room for you, so that the traffic is not suddenly affected. But more than that, you are also telling the drivers around that you are aware of them, and you are not suddenly going to do something stupid.
It has always been amazing to me that some people consider themselves 'good' drivers simply because they can drive fast. Surely, if they want to demonstrate that they are good drivers they should be showing that they are aware of traffic flow, and aware of how other drivers will react to their moves.
So, when you are out on the road, practice courteous driving. All it takes is remembering that driving is not a solo activity. There are other people out there driving their cars. Think about them, how they might be thinking or feeling, and drive so that everyone wins.