3 ideas
Persuasion alternates between opening (bai), drawing the other party out so he reveals his intentions and resources, and closing (he), concealing your own position and sealing agreements. The speaker opens to learn what the other man wants or fears, then closes once he has what he needs, so no argument is advanced before the listener's real disposition is known.
Before speaking, the persuader assesses the other party's wisdom, capability, wealth, strengths, likes and dislikes, and the state of his relationships, the way one weighs goods on a scale. Speech is then fitted to that measure: with the wise speak broadly, with the eloquent speak concisely, with the noble speak of power, and with the timid speak of safety.
The other party's inner state, which cannot be observed directly, shows itself in outward signs: shifts in expression, what he returns to, and how he reacts when provoked or flattered. The persuader deliberately stirs the listener's desires or fears, because a person under strong emotion cannot hide his real feelings, and then reasons back from those signs to the concealed intention.