There are two points here, the preliminary to a period of meditation and preliminary instruction.
Preliminaries to a Period of Meditation
First, at the beginning of every period of meditation, imagine your root guru sitting on a lotus-and-moon seat above your head. His body is radiant and his face happy and smiling as he regards all beings with nonreferential compassion. In him, all the root and lineage gurus are present.
With intense respect and devotion, repeat the lineage prayer if you wish and, in particular, the following prayer a hundred or a thousand times.
I pray for your blessing, my guru, great and completely worthy spiritual friend. I pray that you will cause love, compassion and bodhicitta to arise in my mind.
Then, imagine that your guru descends through the aperture of Brahma and sits in your heart in a pavilion of light, like an open shell. This exercise in intense respect and devotion is known as guru yoga. It is important to begin every period of meditation this way.
Second, with respect to preliminary instructions, if the four contemplations -that is, the difficulty of obtaining a free and well-favored existence, death and impermanence, consideration of the shortcomings of samsara
, and action as seed and result - are new to you, they are fully explained in the graded-path texts. You need to work at these contemplations so that they definitely become part of your thinking. Here is a concise presentation of the basic points for those who would like one.
THE ACTUAL INSTRUCTIONS
In order to obtain the framework for the practice of dharma, this precious human existence, which, in being free and well favored, offers excellent opportunities, one must practice excellent virtue, since this is its karmic seed. Since the proportion of sentient beings that do practice virtue thoroughly is very small, the result, a free and well-favored existence, is difficult to obtain. When one considers the numbers of other sentient beings, such as animals, it is evident that human existence is just a remote possibility. Therefore, you should, above all else, work at dharma wholeheartedly so that the human existence now obtained is not wasted.
Furthermore, since life is uncertain, the causes of death are numerous, and one can't even be sure that death won't come today, one must exert oneself in the dharma right away. At the time of death, except for virtuous and nonvirtuous actions, nothing will follow, not wealth, food, possessions, nor land, body, or status. Since these are not even as helpful as a straw, there is not the slightest need for them.
After death, the power of karma causes one to experience birth in one of the six classes of beings. Whichever it is, there will be nothing but suffering, not even a strand of happiness.
Since happiness and suffering infallibly develop from virtuous and nonvirtuous actions, one should not do anything evil even at the risk of your life. One should practice only virtuous actions with great diligence.
You should energetically train yourself in this kind of thinking. At the end of every period of meditation, perform the seven-branch prayer as many times as you are able to. In postmeditation periods, put the points of your reflections into practice. These instructions apply to all forms of preparation and actual practice.
From The Great Path of Awakening : An Easily Accessible Introduction for Ordinary People by Jamgon Kongtrul, translated by Ken McLeod. Copyright 1993 by Ken McLeod.
Published by arrangement with Shambhala Publications, Inc., Boston.
Page View: 4,289,162
This site provides an on-line database of commentaries on the Tibetan Buddhist meditation practices of lojong (Mind Training) and tonglen.