Take a look at these ‘model sheets.’ They are used in animation studios to make sure all the animators know the size, shape, design, etc. of all the characters they might be animating. That way, if more than one animator works on Stewie from Family Guy (for instance), he’ll look the same no matter who worked on him.
Yours doesn’t have to be that detailed. You may simplify your character something like this:
Walk Cycle and Model Sheet