Feel your feet in contact with the ground. Feel yourself erect, straight, vertical. Move your neck slightly back, so you feel that the cervical region is a prolongation of the rest of your spinal cord. Be aware of the position of your shoulders and shoulder blades. The slightest rising up of the shoulders is a defense. Feel your nostrils. Feel the entrance to your nostrils. Fell the coming and going of the breath several inches in front of the entrance to the nostrils. Do not control the breath or have any pretension of being an observer. Feel the expansion of the breath in the upper part of your torso, on the level of your collarbones. Be completely one with the coming and going of the breath, which is localized on the level of the collarbones. Then feel the expansion of the breath a little lower, in the center, the middle part of your trunk. Now completely ignore the upper part. Be one with coming and going of the breath. Then feel the expanding of the breath in the lower part, the abdominal region. Ignoring the upper and middle regions, go knowingly into the process. Then inhale with all of the regions: lower, middle, upper part; exhale upper part, middle part, lower part. The inhalation and the exhalation take place exclusively through the nostrils.
Let the exhalation go completely to the end. Sometimes you think that you are at the end, but there is still some residue. So go to the very end of the exhalation, but without forcing the air out. Then be completely attuned to the silence after the exhalation, and wait for the inner need of the body to inhale. Feel the exhalation and inhalation several inches in front of the nostrils. There must be no intention in the frontal region of the brain. It then is completely relaxed. There is no rising up of the shoulders. Keep them down, knowingly. There are no gaps or stops and starts in the inhalation and the exhalation; it is one steady flow, from the beginning to end, the same intensity. You live from moment to moment; there is no anticipation to an end. You follow from moment to moment. Be aware during the inhalation that it is not a grasping, a taking. And let the exhalation completely die in silence. There is a moment when there is a forgetting of the inhalation and exhalation, and awareness is in identity with the silence between exhalation and inhalation. Be this identity with the silence.
You can read more from Jean Klein here.