"How to make friends and influence people."
How to Win Friends and Influence People
This is Dale Carnegie's summary of his book, from 1936
http://www.westegg.com/unmaintained/carnegie/win-friends.html
A nice book to read on the power of persuasion and how to best implement it.
Another book I read on this made a quite interesting observation:
"One of the most powerful psychological desires people have is to be right."
Therefore, the book argued, in debates and discussions you should help them to be.
A corollary to this is that if someone is offering you an olive branch, you should accept it, not stomp it into the ground.
Bob Clark