Once seated, roll your hips slightly forward, allowing your belly to relax and your breath to move freely.
Center your spine by gently swaying from left to right in decreasing arcs.
Push the crown of your head toward the ceiling, straightening and extending your spine. Then relax your shoulders.
Your head should not tilt forward or backward or lean to the side. Ears over your shoulders, nose in line with the navel.
Eyes are lowered at a 45-degree angle, looking about three feet in front of you without focusing the gaze. If there is a wall there, look as if you were seeing through the wall.
Lips and teeth should be gently closed, tip of tongue against roof of your mouth behind the front teeth. Swallow and suck the saliva from your mouth, creating a vacuum.
Place your hands in the cosmic mudra, left hand on top of the right, palms up, tips of the thumbs lightly touching, forming a wide oval. Hands should rest on lap, thighs, or lower abdomen, where they do not create a stress on your arms.
The whole point is to find an alert, energetic posture that will allow you to sit very still. Check yourself each time you sit, forming the habit of careful attentiveness to your body posture before zazen.
Breathe in through the nose, letting the air fill your lower abdomen as if it were a balloon, then gently release with a slow, deep out-breath â€¦ in and out, in and out.
Count one on the in-breath, two on the out-breath, three on the in-breath, four on the out-breath, and so on, up to ten. Then begin at one again. If it is more comfortable for you, you may count the out-breaths only and follow the in-breath without counting. If a thought causes you to stray from the counting, just notice that, return your focus to the breath, and begin the count again starting at one.
Although written meditation instructions can get you off to a good start, it is helpful to receive personal guidance from an experienced instructor. Above all, enjoy the experience. A great teacher once said that zazen is the gate of peace and compassion.