How to Win People to Your Way of Thinking – Principle 5
In talking with people, don’t begin by discussing the things on which you differ. Begin by emphasizing—and keep on emphasizing—the things on which you agree. Keep emphasizing, if possible, that you are both striving for the same end and that your only difference is one of method and not of purpose.
Get the other person saying “Yes, yes” at the outset. Keep your opponent, if possible, from saying “No.”
Get the other person saying “yes, yes” immediately.
* Source: How to Win Friends & Influence People by Dale Carnegie