For my daughter, the song needs to be one that she connects to in some way - something that expresses how she feels or that touches her emotions. Because she is a teen, she often picks songs from movies with characters she identifies with and then we listen to the movie soundtrack and piece something together.
She has skated to something from "Harry Potter", something from the animated movie "Spirit", something from "Transformers", and also to "Somewhere Over the Rainbow". I think she is planning on "Phantom of the Opera" or "Pirates of the Caribbean" for her next program. Do you have any favorite classical composers, contemporary music artists or a movie that is a favorite? That may be a good starting place.