As you have seen, animating a walk or a run requires a strong knowledge of weight and balance. Once you've mastered the basics of a walk, you can begin to add character to the walk by playing with the timing and spacing of your character's motions. Mastering these skills takes time and practice, so be sure to animate a lot of different characters walking and running in many different ways.
Chapter One. Basics of Character Design
Chapter Two. Modeling Characters
Chapter Three. Rigging Characters
Chapter Four. Basics of Animation
Chapter Five. Creating Strong Poses
Chapter Six. Walking and Locomotion
Chapter Seven. Facial and Dialogue Animation
Chapter Eight. Animal Motion
Chapter Nine. Acting
Chapter Ten. Directing and Filmmaking