Knowledge about God is not the same as knowledge of God. We can have a systematic theology of God memorized, and still not grow in our knowledge of God.
How can we turn our knowledge about God into knowledge of God? The rule for doing this is simple but demanding. It is that we turn each truth that we learn about God into matter for meditation before God, leading to prayer and praise to God.
We have some idea, perhaps, what prayer is, but what is meditation? Well may we ask, for meditation is a lost art today, and Christian people suffer grievously from their ignorance of the practice.
Meditation is the act of calling to mind, and thinking over, and dwelling on, and applying to oneself, the various things that one knows about the works and ways and purposes and promises of God. It is an activity of holy thought, consciously performed in the presence of God, under the eye of God, by the help of God, as a means of communion with God.
Its purpose is to clear one’s mental and spiritual vision of God, and to let his truth make its full and proper inpact on one’s mind and heart. It is a matter of talking to oneself about God and oneself; it is, indeed, often a matter of arguing with oneself, reasoning oneself out of moods of doubt and unbelief into a clear apprehension of God’s power and grace.
Its effect is ever to humble us, as we contemplate God’s greatness and glory and our own littleness and sinfulness, and to encourage and reassure us—“comfort” us, in the old, strong, Bible sense of the word—as we contemplate the unreachable riches of divine mercy displayed in the Lord Jesus Christ. . . . And it is as we enter more and more deeply into this experience of being humbled and exalted that our knowledge of God increases, and with it our peace, our strength, and our joy. God help us, then, to put our knowledge of God to this use, that we all may in truth, “know the Lord.”
—J. I. Packer, Knowing God (InterVarsity Press, 1993), 23.
This is the biblical—in opposition to popular and mystical—description of meditation: thinking about what God has already said in his word, not waiting for him to say something new especially for you.