Tánpàn qián yào zhījǐ-zhībǐ, liǎojiě duìfāng de dǐxiàn.
Before negotiations, you must know yourself and your opponent, understanding their bottom line.
Tips
history
From Sun Tzu's 《孙子兵法》 (The Art of War, ~5th century BC). The full saying is 知己知彼，百战不殆 - know yourself and your enemy, and in a hundred battles you will never be defeated.
memory
己 (jǐ) = oneself, 彼 (bǐ) = the other. The pattern repeats: 知己 (know-self) 知彼 (know-other). Mirror structure for a mirror concept.
