Creating a ballet in a art it is called choreography.  A choreogragher is a person who creates ballets.  A choreographer can make up new versions of old ballets.  Almost all ballet companies must have a choreographer.  A ballet can tell a story.  New ideas for ballets can come from peoms, a peice of a story,and etc.  The choreographer have to listen to the music that they want to use in their ballet first.  After that is done they work on steps to find what is most comfortable to the dancers.  The choreographers usually start working on the parts for one or two dancers.  Then the bigger groups are done.  After the ballet is finished the steps are written down.  The last thing to do is to design and make the costumes.