In this video Fr. Thomas Keating talks about the foundations of Centering Prayer, a contemporary form of an ancient practice of Christian contemplative practice.
Points to note. Fr. Thomas says first and foremost (in the Christian path), it is a relationship, not a method. The key is the relationship with God within not a technique per se. But as he says, there are certain things that facilitate the relationship.
And within that facilitation--principle #3: when engaged with thoughts ever so gently return to the word.
This video expands on the point:
This is one of the hardest things (I think) to pick up concerning Centering Prayer. Centering Prayer is not a concentrative method--it's not about focusing one's attention on a single focus. The sacred word is not a mantra (as in say a prayer bead practice). In Centering Prayer a person keeps his/her attention in a more receptive state.
Westerners have a very hard time learning meditation. There are so many thoughts and people give up because of the inernal noise. But I love Fr. Thomas' line about having a "jolly attitude" towards one's thoughts. Centering Prayer is an other-powered form of spiritual practice--it is the Spirit within (The Other) that does the work and one cooperates with that process. So the key point is the intention to be fully in the presence and action of God. Thoughts, feelings, sensations are all part of it. Fr. Thomas' point about distractions at the end is really powerful.
Update I: In the first video, Fr. Thomas talks about the four principles of Centering Prayer but only desccibes the first three: 1. choosing a sacred word as the symbol of one's intention to consent to God's presence and action, 2. sitting comfortably with eyes closed slowly introduce the sacred word, 3. when engaged with your thoughts, ever so gently return to the word. The fourth is: at the end of the prayer period remain in silence with eyes closed for a couple of minutes.
Update II: A cool variation on Centering Prayer is to use one's breath rather than a sacred word as the symbol of one's intention to consent to God's present and action. More here from the wonderful David Frenette.