Squash and stretch

The purpose of squash and stretch is to give a sense of weight and flexibility to drawn or computer animated objects. It can be applied to simple objects, like a bouncing ball, or more complex constructions, like the musculature of a human face.

Anticipation

Anticipation is used to prepare the audience for an action, and to make the action appear more realistic.

Staging

This principle is akin to staging, as it is known in theatre and film. This can be done by various means, such as the placement of a character in the frame, the use of light and shadow, or the angle and position of the camera.

Straight ahead action and pose to pose

These are two different approaches to the drawing process. Straight ahead action scenes are animated frame by frame from beginning to end, while “pose to pose” involves starting with drawing a few key frames, and then filling in the intervals later.

Follow through and overlapping action

Follow through and overlapping action is a general heading for two closely related techniques which help to render movement more realistically, and help to give the impression that characters follow the laws of physics, including the principle of inertia.

Slow in and slow out

The movement of objects in the real world, such as the human body, animals, vehicles, etc. needs time to accelerate and slow down. For this reason, more pictures are drawn near the beginning and end of an action, creating a slow in and slow out effect in order to achieve more realistic movements.

Arc

Most natural action tends to follow an arched trajectory, and animation should adhere to this principle by following implied “arcs” for greater realism. This technique can be applied to a moving limb by rotating a joint, or a thrown object moving along a parabolic trajectory.

Secondary action

Adding secondary actions to the main action gives a scene more life, and can help to support the main action.

Timing

Timing refers to the number of drawings or frames for a given action, which translates to the speed of the action on film. On a purely physical level, correct timing makes objects appear to obey the laws of physics.

Exaggeration

Exaggeration is an effect especially useful for animation, as animated motions that strive for a perfect imitation of reality can look static and dull. 

Solid drawing

The principle of solid drawing means taking into account forms in three-dimensional space, or giving them volume and weight. 

Appeal

Appeal in a cartoon character corresponds to what would be called charisma in an actor. A character who is appealing is not necessarily sympathetic; villains or monsters can also be appealing, the important thing is that the viewer feels the character is real and interesting.