I recently had a friend give me a slight nudge toward discernment when considering meditation. He said I should be careful with emptying the mind, because it may leave me open to other less beneficial influences. This is true especially in light of the scriptures telling us to "fill our minds" with the things of God. But it left me wondering if I've given the opposite impression. It's difficult for me to describe what the contemplative life is rather than why it is, because you can do a lot of different "things" to foster it but the point of it is singular: to be before God. But I thought I'd start with describing one thing you can do: centering prayer. It's the most "meditatey" of the meditative exercises and the closest thing to emptying the mind. A good modern source on centering prayer is the work of Father Thomas Keating, a Roman Catholic (but ecumenical) priest. Some older sources that talk about this kind of exercise are The Cloud of Unknowing (anonymous author, 6th century) and A Short Method of Prayer, by Madame Guyon. Centering prayer was also mentioned in a previous post, Transcendental Meditation Information.
In centering prayer, the Christian finds a comfortable, silent place of retreat where he or she can be still. Having already chosen a word on which to center one's mind (most often the name of God), the Christian will begin to allow all the worries and thoughts bombarding their mind to come, as they usually do, in their attempt to disrupt this silence. The name is then thought - thrown up, in a way - into the midst of those disruptions, and the one meditating begins to concentrate on it. A good way to think of this is that the name becomes like a shield, which the mind holds on to in the midst of bombardment from worldly thoughts. Whatever anxieties come become irrelevant in the presence of that name, and the Christian may repeat thinking it or muttering it out loud (if need be) until it is all that is left in the mind and there is only silence beside it.
It is emptying the mind, but one empties it of all thoughts other than God or Christ. It is not, however, emptying the mind completely or emptying it permanently, for Christ becomes the all that the mind clings to in order to achieve stillness. Centering prayer is also not the end. Once centered, the Christian can then begin to dialogue with God in other forms of prayer: meditating on scripture, petitioning God with requests, praising Him, listening prayer, or journaling. Centering prayer first says to Him, "I have set aside all my worries and anxieties to be with You. I am without distraction, and all my thoughts are in You now. Let's spend some time together."
For me, it takes about 20 minutes to get "centered" in this way. Some, who have practiced this for years, can quiet their minds in a couple of minutes. Like anything else, the more one practices letting go of the "to do" lists, the worries, the questions, and centering the mind on God's presence, the easier it becomes.