Neck tension can be reduced through the right work of the arms and shoulder girdle. In class we learn to direct the movement of the arms correctly and to do poses using wall ropes. They give extra support and help improve the mobility of the shoulder girdle, free the shoulders and reduce unnecessary tension in the neck.
A simple exercise at home: Utthita Parshva Hastasana. Stand side-on to the wall and press your palm against it at shoulder height. Keeping the shoulder low, breathe calmly for a few cycles. Then repeat with the other arm.
This simple exercise helps you feel the work of the arm and shoulder and gently release tension in the neck and shoulders.