http://en.wikipedia.org/wiki/How_to_Win_Friends_and_Influence_People
The most important for me is to _never_ argue. There is no way to win an argument.
Forum is a good example. Nobody change theirs mind here. Just get more sure about their point of view. Then get angry at people with different opinion.
Giving another arguments make them more sure about their point of view and dislike you more at the same time.
I post on different forums for years and I'm not sure if I've seen 1 person who changed their mind and was grateful for that.
I'm shocked myself I haven't noticed this before and was keep trying to convince people for years.
I think you are overdoing it there. It happens all the time. In the micro: My wife and I talk about where we might go for dinner and come to some compromise decision. In the macro: the nation argues it out and decides to change the laws on marijuana or gay marriage.
However, influence doesn't necessarily mean total control as in winning or losing an argument. It can mean helping to shape the debate or leading someone to a more informed decision. In short, I'd say it was about techniques that allow you to be heard, not obeyed.