The second element we need for prayer is energy. We have connected the telephone wire, now we need to send an electric current through it.

In prayer, the electric current is love, mindfulness, and right concentration. Mindfulness is the real presence of our body and our mind. Our body and our mind are directed toward one point, the present moment. If this is lacking, we are not able to pray, no matter what our faith. If you are not present, who is praying?

To pray effectively, our body and mind must dwell peacefully in the present moment. When you have mindfulness, then you have concentration. This is the condition that will lead to prajna, the Sanskrit word for insight and transcendent wisdom. Without that, our prayer is just superstition.

The Energy of Prayer 
Thich Nhat Hanh 
Berkeley: Parallax Press, 2006, pp 43-44 

There is only one basic rule for prayers alone: Make sure you are left alone. Once this is assured, it will be quite easy to find your own expression of whatever it is that fills your heart at that time. But being left alone in prayer is not as easy as one might think. Especially in religious communities, there are sometimes those whose religious observance consists largely in observing others. When and where and how you say prayers, for how long and what posture—every detail is apt to come under scrutiny. It may be a great blessing to be able to discuss all these points with a teacher of prayer who will guide us to find what is most helpful for us personally. Beyond that, we have a right and a duty to insist: Concerning my prayers alone, leave me alone. 

Yes, we have a duty in this respect. The most frequent interference does not come from the outside, but from within ourselves; it is not restricted to those living in communities, but all of us have to struggle against it. There is within each of us, I suspect, that little voice that will not leave us alone. It keeps urging us to conformity with some arbitrary model of prayer, or to non-conformity. In either case we get preoccupied with the model that we imitate or reject, instead of facing the challenge to be creative in our prayers alone. You are unique. If your prayer is genuine, it will be the grateful expression of your uniqueness.
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Gratefulness, The Heart Of Prayer: An Approach To Life In Fullness 
by Brother David Steindl-Rast
New Jersey: Paulist Press, 1984
Page 53
 
Brother David Steindl-Rast, O.S.B., has written several books on the contemplative life and has given lectures in the United States, Europe, and Asia. Born in Vienna, he studied art, anthropology, and psychology there, holding degrees from the Vienna Academy of Fine Arts and the University of Vienna. In 1953 he joined the Benedictine monastery of Mount Saviour in Elmira, N.Y. He has been involved in monastic renewal in the United States and in the dialogue of Oriental and Western spirituality.

Is prayer a form of talking? Must it involve words? A woman wrote to me, "I feel a deep desire to pray, but I cannot bring myself to use words. They seem unnecessary and silly." Oscar Wilde had similar doubts about his words. He once wrote, "I do not talk to God so as not to bore him."

In its simplest form, prayer is an attitude of the heart — a matter of being, not doing. Prayer is the desire to contact the Absolute, however it may be conceived. When we experience the need to enact this connection, we are praying, whether or not we use words. 

That doesn't mean words are wrong. People are often inspired to express verbally their unity with God, Goddess, the Divine, the Universe, the Absolute in some way — to lift their voices in words or song. If we need to use words, we should use them. But the essence of prayer is not something you say on Sunday morning, before meals, or at bedtime. The essence of prayer bypasses all the “Our Fathers” and “Hail Marys” and goes beyond all thethees and thous….

…we can expand the definition of prayer:
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     Prayer is communication with the Absolute.

This definition is deliberately broad. It allows people to find communication any way they see fit. It also invites them to image the Absolute in their own way — including the idea that the Absolute is both transcendent and immanent, "out there" as well as "in here."
In prayer, people may fill in the blanks anyway they choose.


Prayer is Good Medicine 
by Larry Dossey, M.D. 
New York: Harper Collins, 1997
pages 83-85

Larry Dossey, M.D., is the former chief of staff at Humana Medical City Dallas and former co-chair of the panel on mind/body interventions for the National Institutes of Health. He is the author of many books, including Healing Words, Recovering the Soul, and Meaning and Medicine.

…Prayer is either petitional or in it's wider sense is inward communion. In either case the ultimate result is the same. Even when it is petitional, the petition should be for the cleansing and purification of the soul, for freeing it from the layers of ignorance and darkness that envelop it. He, therefore, who hungers for the awakening of the divine in him must fall back on prayer. But prayer is no mere exercise of words or of the ears, it is no mere repetition of empty formula. Any amount of repetition of Ramanama [God’s Name] is futile if it fails to stir the soul. It is better in prayer to have a heart without words than words without a heart. It must be in clear response to the spirit which hungers for it. And even as a hungry man relishes a hearty meal, a hungry soul will relish a heartfelt prayer. And I am giving you a bit of my experience and that of my companions when I say that he who has experienced the magic of prayer may do without food for days together but not a single moment without prayer. For without prayer there is no inward peace.


Prayer
Mohandas K. Gandhi 
edited by John Strohmeier 
Berkeley: Berkeley Hills Books, 2000, p. 23

Anthony Bloom writes about kavanah (honesty, sincerity and focus) from a Christian perspective.

I have tried to point out, first of all, that your prayer must be turned inwards, not towards a God of Heaven nor towards a God far off, but towards God who is closer to you than you are aware; and secondly, that the first act of prayer is to choose such words of prayer as are completely true to what you are, words you are not ashamed of, which express you adequately and are worthy of you—and then offer them to God with all the intelligence of which you are capable. You must also put all the heart you can into an act of worship, an act of recognition of God, an act of cherishing, which is the true meaning of charity, an action which involves you in the mind, in the heart, and an action which is completely adequate to what you are. The first thing which I suggest, therefore, is that you should ask yourself what words of prayer make sense for you to offer to God, whether they be your own words or those of other people. Ask yourself also how much they touch your heart, to what extent you are capable of concentrating your mind on them – for if you cannot be attentive to the word you say, why should God? How can He receive them as an expression of love if you do not put your heart into them, if you have only put in a certain amount of courtesy together with a certain amount of absent-mindedness? And then if you learn to use a prayer you have chosen at moments when you can give all your attention to the divine presence and offer God this prayer, gradually what happens is that the awareness of God grows within you to such an extent that whether you are with people, listening, speaking or whether you are alone working, this awareness is so strong that even if you are with people you will still be able to pray.

Anthony Bloom was founder and for many years bishop - then archbishop, then metropolitan - of the Diocese of Sourozh, the Patriarchate of Moscow's diocese for Great Britain and Ireland. As a bishop he became well known as a pastor, preacher, spiritual director and writer on prayer and the Christian life.

Beginning to Pray
by Anthony Bloom
Paulist Press: 1970, New York
Page 49