Obscurity Rules
Obscurity rules are important but should also be used sparingly. If the
person who is it is given a name by a player that they think couldn't be
known by any reasonable human being, then they can call obscurity
(for example, the brother of the wife of the blacksmith who shoed
Washington's gray horse). This rarely happens in party play, since it is
usually a result of someone listening in to the radio broadcast and
looking up names in a book (that behavior is frowned upon).
There are also obscure clues. For example, "I am in a movie which has
the same name as the title character in an Italian opera set in a city
which is featured in a 1985 movie directed by the man who directed an
almost identical movie ten years later." No human being can be
expected to parse this, much less know it."
Choosing good names (for "it")
A good name is known by everyone in the room.
A good name springs readily to mind (for example, Robert
Maplethorpe was used in a recent game: although it was known by
many people, it did not readily spring to mind).
Keep in mind that people can only ask yes and no questions and it will
take them a while to arrive at the name.
Use names that you can answer questions about easily.