If you choose the breath as your focal point, make yourself fully aware of each in-breath and each out-breath. Notice the sensation created by the breath’s movement and fix your attention on the point where that feeling is most prominent; where the sensation of the breath is felt most acutely: for example, the tip of the nose. Make sure you know when the breath comes in and when it goes out, but don’t follow its course—simply focus on the spot where it passes through. If you find it helpful, combine your breathing with a silent repetition of buddho, thinking 'bud' on the point of inhalation and 'dho' on the point of exhalation. Don’t allow errant thoughts to interfere with the work you are doing. This is an exercise in awareness of the present-moment; so remain alert and fully attentive.
As mindfulness gradually establishes itself, the mind will stop paying attention to harmful thoughts and emotions. It will lose interest in its usual preoccupations. Undistracted, it will settle further and further into calm and stillness. At the same time, the breath—which is coarse when you first begin focusing on it— gradually becomes more and more refined. It may even reach the stage where it completely disappears from your conscious awareness. It becomes so subtle and refined that it fades and disappears. There is no breath at that time—only the mind’s essential knowing nature remains.