Find out each person’s thumbscrew—what he likes, and what motivates him to do things.  It is the means of setting his will in action. 

       You must know where to get at anyone.  Every choice has a special motive that varies according to taste.  All people idolize something—for some it is fame, for others self-interest, for most it is pleasure.  Skill consists in knowing these idols in order to bring them into play.

       Know a person’s mainspring of motive, and you will possess the key to his will.  Utilize his primary motives, which are not always the highest, but more often the lowest part of his nature. 

       Observe and examine a person’s ruling passion, appeal to it with words, set it in motion by temptation, and you will always checkmate his freedom of will.