Squash and stretch
the purpose of squash and stretch is to give a sense of weight and flexibility to drawn objects. It can be applied to simple objects, like a bouncing ball.
anticipation is used to prepare the audience for an action, and to make the action appear more realistic. A dancer jumping off the floor has to bend his knees first.
The purpose of staging is to direct the audience’s attention, and make it clear what is of greatest importance in a scene. This can be done by various means, such as the placement of a character in the frame, the use of light and shadow, and the angle and position of the camera. The essence of this principle is keeping focus on what is relevant, and avoiding unnecessary detail.
Straight ahead action and pose to pose
“Straight ahead action” means drawing out a scene 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. pose to pose is mostly used nowadays since computers help animators to fill the intervals.