Listen to the person you need to convince of anything. Highlight the manner of his speaking and speak. His vocabulary, which he conveys to you is a priceless weapon against it, and accidentally dropped the word can be a very powerful argument in dispute, and in the belief.
Make adjustments - take the pose, the mirror, or like the pose of the source, and synchronize breathing or gestures with his breathing and gestures. This will help you subconsciously cause him resist your arguments, because on a subconscious level you will be copying it.
Identify his weaknesses and words-parasites, which can reveal his uncertainty about certain words. Use clarification in order to confuse your opponent while avoid direct confrontation on a personal level. The advantage is if your conversation is going to happen in public - the pressure of other people on your buddy will help you develop the situation in the wrong direction, which is convenient to you.