Universally Recommended Instructions for Zazen (Fukan zazengi 普勧坐禅儀)

The way is originally perfect and all-pervading. How could it be contingent on practice and realization? The true vehicle is self-sufficient. What need is there for special effort? Indeed, the whole body is free from dust. Who could believe in a means to brush it clean? It is never apart from this very place; what is the use of traveling around to practice? And yet, if there is a hairsbreadth deviation, it is like the gap between heaven and earth. If the least like or dislike arises, the mind is lost in confusion. Suppose you are confident in your understanding and rich in enlightenment, gaining the wisdom that knows at a glance, attaining the Way and clarifying the mind, arousing an aspiration to reach for the heavens. You are playing in the entrance way, but you are still short of the vital path of emancipation.

Consider the Buddha: although he was wise at birth, the traces of his six years of upright sitting can yet be seen. As for Bodhidharma, although he had received the mind-seal, his nine years of facing a wall is celebrated still. If even the ancient sages were like this, how can we today dispense with wholehearted practice?
Therefore, put aside the intellectual practice of investigating words and chasing phrases, and learn to take the backward step that turns the light and shines it inward. Body and mind of themselves will drop away, and your original face will manifest. If you want to realize such, get to work on such right now.
For practicing Zen, a quiet room is suitable. Eat and drink moderately. Put aside all involvements and suspend all affairs. Do not think "good" or "bad." Do not judge true or false. Give up the operations of mind, intellect, and consciousness; stop measuring with thoughts, ideas, and views. Have no designs on becoming a buddha. How could that be limited to sitting or lying down?
At your sitting place, spread out a thick mat and put a cushion on it. Sit either in the full-lotus or half-lotus position. In the full-lotus position, first place your right foot on your left thigh, then your left foot on your right thigh. In the half-lotus, simply place your left foot on your right thigh. Tie your robes loosely and arrange them neatly. Then place your right hand on your left leg and your left hand on your right palm, thumb-tips lightly touching. Straighten your body and sit upright, leaning neither left nor right, neither forward nor backward. Align your ears with your shoulders and your nose with your navel. Rest the tip of your tongue against the front of the roof of your mouth, with teeth together and lips shut. Always keep your eyes open, and breathe softly through your nose.
Once you have adjusted your posture, take a breath and exhale fully, rock your body right and left, and settle into steady, immovable sitting. Think of not thinking, "Not thinking ––what kind of thinking is that?" Nonthinking. This is the essential art of zazen.
The zazen I speak of is not meditation practice. It is simply the dharma gate of joyful ease, the practice realization of totally culminated enlightenment. It is the koan realized; traps and snares can never reach it. If you grasp the point, you are like a dragon gaining the water, like a tiger taking to the mountains. For you must know that the true dharma appears of itself, so that from the start dullness and distraction are struck aside.
When you arise from sitting, move slowly and quietly, calmly and deliberately. Do not rise suddenly or abruptly. In surveying the past, we find that transcendence of both mundane and sacred, and dying while either sitting or standing, have all depended entirely on the power of zazen.
In addition, triggering awakening with a finger, a banner, a needle, or a mallet, and effecting realization with a whisk, a fist, a staff, or a shout ––these cannot be understood by discriminative thinking; much less can they be known through the practice of supernatural power. They must represent conduct beyond seeing and hearing. Are they not a standard prior to knowledge and views?
This being the case, intelligence or lack of it is not an issue; make no distinction between the dull and the sharp-witted. If you concentrate your effort single-mindedly, that in itself is wholeheartedly engaging the way.
Practice-realization is naturally undefiled. Going forward is, after all, an everyday affair.
In general, in our world and others, in both India and China, all equally hold the buddha-seal. While each lineage expresses its own style, they are all simply devoted to sitting, totally blocked in resolute stability. Although they say that there are ten thousand distinctions and a thousand variations, they just wholeheartedly engage the way in zazen. Why leave behind the seat in your own home to wander in vain through the dusty realms of other lands? If you make one misstep, you stumble past what is directly in front of you.
You have gained the pivotal opportunity of human form. Do not pass your days and nights in vain. You are taking care of the essential activity of the buddha-way. Who would take wasteful delight in the spark from a flintstone? Besides, form and substance are like the dew on the grass, the fortunes of life like a dart of lightning ––emptied in an instant, vanished in a flash.
Please, honored followers of Zen, long accustomed to groping for the elephant, do not doubt the true dragon. Devote your energies to the way of direct pointing at the real. Revere the one who has gone beyond learning and is free from effort. Accord with the enlightenment of all the buddhas; succeed to the samadhi of all the ancestors. Continue to live in such a way, and you will be such a person. The treasure store will open of itself, and you may enjoy it freely.

-from SotoZen.Net (http://global.sotozen-net.or.jp/eng/zazen/index.html)