Thumbnailing is the process of an animator sketching out their ideas for a character or putting up a scene. Thumbnailing is the first stage of animation and is used to get feedback from the creator. Doing it initially decreases the project's chances of being changed after hours and expertise being wasted on a project. While this is primarily used in 2D animation, the merits hold true for 3D animators as well to breakdown the movements of each scene.
This book gives you 101 pages of thumbnailing templates to help breakdown your scene. Use one book for each project, or for each character to keep track of the breakdowns.
Each page can be easily drawn on with lined areas for the drawings, timeline for keyframes, and a blank section for notes.