Punctuality
Now initially as I think of being punctual, I consider it a trait that most professions expect from you. It springs to mind in this instance though because in general as a Ballet dancer you have been trained and are expected to be highly disciplined. Where I feel the matter applies specifically to the ballet world though is that if I were to be late for a rehearsal for example, that would have a knock on effect for my colleagues. In a standard office job, one could be late and although it would be frowned upon for the sake of work etiquette, it's possible that no one else is directly affected. In a ballet company, rehearsals often revolve around teamwork and cooperation. My colleagues rely on my presence as I rely on theirs. If I were to be late, not only would it be rude, I'd be letting my colleagues down.
Conditioning
Ballet is a highly skilled profession. In order to work as a dancer, one must take great care to maintain the state of the body with the aim of injury prevention and also maintaining a high standard of fitness in order to practice dance effectively. In many dance companies it is considered ethical to take responsibility of this yourself as a company won't necessarily 'babysit' you. Examples of this would be having regular massages, warming up before rehearsals and attending training class in the mornings.
Commitment to a Role/Piece
The first two things I mentioned are quite simple and basic examples of ethics. Also things that are arguably standard considerations of any practitioner. This last point covers an artist's responsibility of maintaining a director/choreographers vision. Looking after your body and turning up on time are all things that combine and lead up to putting on a great performance, and the performance is the ultimate goal for a dancer. When a choreographer has an idea, they will begin to work on and develop their piece. As a dancer it's easy to be a critic but ethically it's not your place to put in more or less effort based on your personal feelings. It is up to you to perform to the best of your ability and let the audience decide for themselves if they enjoy a certain work.