Use selective honesty and generosity to disarm your victim: one sincere and honest move will cover over dozens of dishonest ones. Open hearted gestures of honesty and generosity bring down the guard of even the most suspicious people. Once your selective honesty opens a whole in their armor, you can deceive and manipulate them at will. A timely gift — a Trojan horse — will serve the same purpose.
How very Machiavellian this purports to be. Anyone who pays attention and has reasonable political skills will see right through those who would do this to you. Deception is such an overt act. I would suggest that discretion would be a better tool and it is much less offensive to selective honesty.