1. The lowest grade is that of petitionary prayer for material benefits. One asks for mundane benefits whether for oneself, or, as in the case of intercessionary prayer, for another. In its crassest forms it borders on idolatry and superstition. A skier who prays for snow, for example, makes of God a supplier of mundane benefits, and this amounts to idolatry, the worshipping of a false god.
As for supersition, consider the case of a believer who places a plastic Jesus icon on the dashboard of her car. It seems clear than anyone who believes that a piece of plastic has the power to ward off automotive danger is superstitious. A hunk of mere matter cannot have such magical properties. Superstition in this first sense seems to involve a failure to understand the causal structure of the world or the laws of probability. A flight attendant who attributes her years of flying without mishap to her wearing of a rabbit's foot or St. Christopher's medal is clearly superstitious in this first sense. Such objects have no causal bearing on an airplane's safety.
But no sophisticated believer attributes powers to the icon itself. The sophisticated believer distinguishes between the icon and the spiritual reality or person it represents.
Well, what about the belief that the person represented will ward off danger and protect the believer from physical mishap? That belief too is arguably, though not obviously, superstitious. Why should the Second Person of the Trinity care about one's automotive adventures? Does one really expect, let alone deserve, divine intervention for the sake of one's petty concerns?
But what if the icon serves to remind the believer of her faith commitment rather than to propitiate or influence a godlike person for egoistic ends? Here we approach a form of religious belief that is not superstitious. The believer is not attributing magical powers to a hunk of plastic or a piece of metal. Nor is she invoking a spiritual reality in an attempt to satisfy petty material needs. Her belief transcends the sphere of egoic concerns.
2. The next grade up is petitionary prayer for spiritual benefits. At this level one is not asking for one's daily bread, but for acceptance, equanimity, patience, courage, and the like in the face of the fact that one lacks bread or has cancer. "Thy Will be done." One asks for forgiveness and for the ability to forgive others. One prays for a lively sense of one's own manifold shortcomings, for self-knowledge and freedom from self-deception. One prays, not to be cured of the cancer, but to bear it with courage. One prays for the ability to see one's tribulations under the aspect of eternity or with the sort of detachment with which one contemplates the sufferings of others.
3. Higher still, I should think, is prayer that is wholly non-petitionary. At this level one asks neither for material nor for spiritual benefits. One form of this is prayer is sheer gratitude for what one has. Prayer as thanskgiving. Beyond this there is prayer as pure aspiration, as a straining of the soul upwards. A pure spiritual seeking, ascending, soaring. One seeks to elevate oneself above one's perceived infirmity and wretchedness. One seeks to rise above the paltriness, crudity, baseness of one's usual thoughts and emotions. Not a petitioning, but a self-elevating and a leaving of oneself behind.
4. Prayer as aspiration may then lead on to forms of meditation proper and perhaps infused contemplation. At the stage of meditation the soul enters mental silence and rests there having abandoned all petitioning and aspiring. Oneis no longer working but resting in mental silence. Within this silence one perhaps receives mystical grace which comes from without the mind.
5. I don't know quite what to do with Weilian prayer. See Simone Weil, Gravity and Grace, Routledge 1995, p. 19: "A method of purification: to pray to God, not only in secret as far as men are concerned, but with the thought that God does not exist." Is this the purest form of prayer, prayer bereft of every petition, bereft even of the hope of attaining anything at all, or is this form of prayer but an expression of Weil's extremism?