Sit or stand tall with your shoulders relaxed and down, away from your ears. Drop your chin straight toward your chest, letting the back of your neck lengthen and stretch. Rest your hands lightly on the back of your head if you want a touch more pressure, without pulling or forcing it down. Keep your shoulders still and square rather than letting them round forward to chase the stretch. Breathe slowly and let your neck relax into the position rather than tensing against it. Turning your chin slightly toward one shoulder before dropping it forward shifts the stretch a little to that side, worth trying if one side of your neck feels tighter than the other.