If I walk, my shadow walks.

(Use two fingers, in walking motion)
If I run, my shadow runs

(Same fingers in running motion)
And when I stand still, as you can see

(Same fingers, standing still)
My shadow stands beside me.

(Use first two fingers on other hand and stand beside the first two fingers) 
When I hop, my shadow hops,

(First two fingers, hopping)
When I jump, my shadow jumps

(Same fingers, jump)
And when I sit still, as you can see,

(same fingers, bend at knuckles to sit.)
My shadow sits beside of me,

(Use as before, both sets of fingers sitting beside each other. )

Source: http://www.preschooleducation.com/sgroundhog.shtml