The 12 principles of animation are;
Squash and stretch is considered the most important principle as it gives a sense of weight and flexibility to object and can be used in a extreme way to give a comical way.
Anticipation is used to prepare for the action for example bending knees to jump or pulling a arm back to throw a object forward.
Staging is used to direct the audiences attention and make sure the important scene is clear whether that idea is an action a mood etc.
Straight ahead action and pose to pose are two different approaches to drawing, straight ahead is drawing out a scene frame by frame start to finish, and then pose to pose is drawing a few key frames and then filling in the rest.
Follow through and overlapping action is used to render movement more realistically and makes sure the objects and characters follow the laws of physics and that different body parts move at different rates like arms from the torso.
Slow in and slow out is the movement of body parts and the time they take to accelerate and slow down after a movement as seen in standing, sitting or running and many more.
Arc is the arched trajectory after the action like a swinging arm, this technique can be used when moving limbs or throwing objects.
Secondary Action is the act of adding more actions to the main action to give the scene more life, a example of this is a person walking which would be the first animation and then their arms swaying being the second.
Timing refers to the number of drawing or frames given for a action, which translates to the speed of the action.
Exaggeration is a effect of animation that can make a scene form into a particular style depending on the level of exaggeration, in short its used to make scenes less dull and static.
Solid drawing is talking about giving the drawings three dimensional and or giving them volume and weight, this can be one of the hardest principles to perfect.
Appeal is the charisma in the character, for example if a character isn’t charismatic they may not be sympathetic and considered a villain and can be used to make the audience feel a certain way.