When bending forward avoid letting the hips fall back behind the heels, and avoid letting the barre elbow point upward toward the sky when bending forward.
When arcing toward or away from the barre avoid letting the hips fall back behind your heels.
When arcing backward and around avoid letting the hips push forward when bending backward, and avoid dropping weight into the lower back (lumbar region of the spine). Also, maintain a supported head to avoid putting pressure on the neck (cervical region of the spine). Let the upper body bend backward and away from your center.
The concepts of en dehors and en dedans may be applied to movement of the leg, the body or the direction of a turn.
To perform cambré en rond en dedans (aka circular port de bras):
To perform cambré en rond en dehors (aka reverse circular port de bras):