--Learn the song and use any movement you want. It is easier to rein in than to do the reverse.
--Then each time you run through the song, cut something. When it gets to the point where it becomes false, you ought to be doing very little with your body, but enough to get the meaning and your POV across.
--Also speak the lyric. Tell the story in conversational tones. What does your body instinctively do? That is your truth.
--What does the song say? What do you want to say using the song? Why are YOU singing this song? Find a Point of View. Have a reason for every movement, pause, emphasis and inflection.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher