There's a great episode in Game of Thrones where Tyrion Lannister using this technique. He tells the three least trustworthy members of Court (The Grand Maester, the Spider and Littlefinger) three different plans of his with promises of: "I'm telling only you and I trust you." Really to see which one tells his sister, and then he can figure out who the rat was by which story his sister gets angry at him for.

It was the grand maester....