A. Consequences are most effective when predetermined by the parents and children when everyone is calm. They should be stated positively and should be specific. Consequences should relate somehow to the misbehavior, not the attitude. Finally, there must be follow-through and consistency.
Parents have to choose which battles are the most important for themselves and for the child.
Then walk away. My caveat is never to argue with teens. We adults always lose. Don't take their behavior personally. Keep your respect for them even if they act disrespectfully to you.