The 12 Principles of Animation
As developed by the 'old men' of Walt Disney Studios.
1. Squash and stretch
The illusion of adding weight and volume to a character as it moves.
Prepares the audience for a major action the character is about to perform. Each major action is proceeded with specific moves that anticipate the audience what is about to happen.
The presentation of an idea so that it is clear.
4. STRAIGHT AHEAD & POSE-TO-POSE
Pose-to-pose is charted with key drawings done at intervals throughout the scene. Straight ahead animation starts at the first drawing, and works drawing-to-drawing to the end of the scene.
5. FOLLOW THROUGH & OVERLAPPING
When the main body of the character stops, all other parts continue to catch up to the main mass.
6. SLOW IN & SLOW OUT
As the action starts, we have more drawings near starting pose, one or two in the middle, and more drawings near the end pose. Few drawings make the action faster, and more actions make the drawing slower.
All actions with few exceptions follow an arc or slightly circular path. Arcs give animation a more natural action, and better flow.
8. SECONDARY ACTION
It's an additional action in a scene used as a supplement of the main action in order to reinforce it, and add more dimension.
More drawings between poses slow and smooth the action. Fewer drawings make the action faster and crisper. Timing maintains the appearance of an object abiding by the laws of physics.
Remain true to reality, just presenting it in a wilder, more extreme form.
11. solid drawings
Taking into account forms in 3-dimensional space; giving them volume and weight.
It's a quality of charm; able to please the viewer's eye. It's the charisma of the action.