The secret to this game is to start the game with only two players knowing the "secret". One of the two must host the game and the other is "it" and must leave the room out of ear shot. The host then has the group decide upon an object in the room. When "it" returns to the room he/she must guess the object and they always manage to guess correctly. Here's how it works.
After the group decides on a object (let's use a piano as an example), the host calls "it" back into the room using one of four ways.
2 all right
3 come on
Note that the first letters of these words spell the name of the game. Let's say in this case, the group decides on the piano as the object and the host calls "it" into the room by saying "come on". Then the host will call out four objects from the room including the chosen object. For example, they might say, "Here are the four objects - the lamp, the window, the piano and the book". "It" immediately says "the piano" since the piano was the third object in the list and "come on" is the code word for #3.
If the host called "it" into the room with "ready", "it" would know that the chosen object would be first in the list of four and so forth.
The object is to continue the game with the same person being "it" and going in and out until someone wants to guess. They then become "it" and go out of the room. When they return, if they guess correctly they can whisper their guess into the ear of the host and the host will announce whether they guessed how the game works. If they didn't guess correctly the game continues with the original "it" or perhaps "it" and the host can switch places.