Wow, I never really understood what meditation was for, nor why I should ever do it.
The main idea is this: Leave space to think and ponder things. Without this, especially in our world, your mind will eventually become a mess of thoughts with no meaning.
He says that meditation "very simply, is the ability to hear God's voice and obey his word." He also differentiates meditation from Eastern religion to explain that
"Christian meditation goes far beyond the notion of detachment...detachment is not enough; we must go on to attachment. The detachment from the confusion all around us is in order to have a richer attachment to God. Christian meditation leads us to the inner wholeness necessary to give ourselves to God freely."
Meditation, by his definition ends up being the means by which God speaks to you. As you clear away distractions and listen to God, you'll find you hear him clearly and can then obey his leading. He goes on to explain that meditation can be combined with the imagination because God "uses images we know and understand to teach us about the unseen world of which we know so little and which we find so difficult to understand."
Finally he goes into explaining that we should meditate on four main things: Scripture, our minds, nature, and the world/age we live in. Scripture is obvious and he goes into ideas about how to study it, focusing on small (one verse) portions. Our minds are something we should "re-collect" and he gives a process of releasing anxieties, bitterness, unforgiveness, etc. through a process of prayer and declaration. Nature is suggested because meditation on nature allows you to reflect on what God made. He says
"Look at the trees...take a flower and allow its beauty and symmetry to sink deep into your mind and heart...sometimes God reaches us profoundly in these simple ways if we will quiet ourselves and listen."
Finally he says to meditate on the "...events of our time." He says "We have a spiritual obligation to penetrate the inner meaning of events, not to gain power but to gain prophetic perspective."
All of this is to help us reorient our minds to hear God's voice and obey what he says to do or think about. By steady and consistent meditation we can do just that.