Meditating is a way of being aware of the light of God that is at the heart of life, and, in being aware, to be renewed in that light within ourselves. Begin your meditation by finding the right position, whether that be seated with your feet on the floor or lying on your back or walking. There is no "correct" position as such, apart from what is right for you. It is important, however, to have your back straight and to be alert within yourself.
In the Celtic tradition the practice of prayer often is pursued in the context of creation. If it is not possible for you to be outside, you may wish to meditate by an open window or in a space in which you can be aware of the elements of creation. The other possibility is to include a bowl of water, for instance, or plants or stones in your door place of prayer — symbols that can help make the connection between a prayerful awareness of God and the mystery of creation.
Begin to repeat silently the words derived from Psalm 43, "Send out your light; let it bring me to your dwelling." At the same time allow images and memories of light to be recalled within you.
It can be helpful to allow your breathing to set the rhythm of repetition. Try saying the words, "Send out your light," as you breathe upwards. Feel your body expanding. Know that in prayer we are opening ourselves to the One who dwells at the heart of life. The light that we are seeking issues up from within. Then as you breathe downwards repeat the words, "Let it bring me to your dwelling." Allow yourself to experience being led to the heart of light within you. Repeat these words meditatively for 15 minutes as you breathe in and out. Whenever distraction occurs, as it always does, simply return to the phrase as a way of focusing your inner attention.
After the 15 minutes of meditation, begin to express silently the prayers of your heart. What are the desires that God has planted in the depths of your being? Express these simply in prayer. Know that your deepest yearnings arise from the image of God within you. Allow them to awaken in you a sense of the longings for life and love that are in men and women throughout the world. For about five minutes pray for them as well. You may wish to complete your time of silence by saying the Lord's prayer or other closing words.
If you are meditating with others it can be helpful to share together some of what you have experienced in the silence. This is not a time for discussion but simply for listening to one another. Often it is in trying to give expression to our experiences of silence that we begin to comprehend what it was that was happening within us during meditation.— John Philip Newell in The Book of Creation: An Introduction to Celtic Spirituality