Blue book

blue book, n., v. 1. the practice of recording character interaction that takes place outside of the play session; usually done in loose-leaf notebooks, and takes its name from the writing assignments often done in writing classes. 
2. the notebook used for bluebooking, regardless of its actual color. [MC]
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Addendum: Blue booking can be a good method to more fully flesh out characters and is looked upon highly by more serious role-players. This method was invented by the legendary game designer Aaron Allston, but has since made it's way into several official game supplements. [MC]