How it moves is more important than what moves.
Though what moves is important, in relative order of importance, it is how it moves that is the important thing...
What the animator does on each frame of film is not as important as what he or she does in between.
" Beautiful models are great, fantastically detailed textures are marvelous, but all is for naught if the movement is unbelievable and stale.
There are so many intricacies to animation that the topic deserves a library dedicated to the art.
Many of these intricate details can only be learned through intensive study of real life, footage, and the work of past animation masters.
There are, however, a few very important ideas that will assist in creating good animation as you start out.
Your 3D application will set in-between frames between keyframes that define where the object should be at every point in the animation.
Although often the computer's interpolation is in a rounded path, it tends to choose the shortest path between two keyframes.
For example, if you are animating a head turning from side to side, and you set a keyframe at the point where the head is looking one direction, and another keyframe when the head is looking the other direction, the computer's guess of interpolation is a direct curve in the shortest path.
Unfortunately, organic motion is rarely in a straight path.
Almost always, our motions take place in arcs or curved arcs.
This dip in the head-turning process is typical of adjustments that need to be made in organic 3D animation.
Keep in mind that although your 3D application is fairly good at making curved paths, these curved paths are often inaccurate to portray good movement.
Although keyframe economy is good (do not insert more than are needed), do not cheat your movement by not giving enough keyframes to define good, believable movement.