Acting and Story
The characters that you animate are the storytellers. They need to convey the script to the audience in a convincing and entertaining manner. The greatest story in the world will be ruined if told by a poor storyteller. To make the story jump off the screen, you need to understand the story, the story structure, and how each scene moves the story forward.
Each scene has an objective, a point that it needs to get across. Each character within the scene also has an objective. A policeman wants to take the criminal to jail. The criminal's objective is freedom. How these two objectives work out determines how the story progresses, If the criminal escapes, you have "The Fugitive." If he goes to jail, you have a different story. When you are animating a scene, be clear on your character's objective and how it affects the story.