We have talked about this method on a few times. Some might call this extemporaneous preaching in that the preacher does not necessarily know what will be preached or how. The preacher prepares by immersing his or herself in the scripture. You take a walk around the scriptural area and simply look around. Memorize the text, read up on all the characters, read up on the location. You want to really know the text. Then you want to really know the people you are addressing. What are their concerns? What are their questions?
There are two types of preachers who employ this method. There are those who have no idea how the sermon will open, proceed, or close. These preachers simply get up and allow the Spirit and their preparation to guide them. The sermon’s point emerges while the sermon is being preached. Now you do practice the sermon, but you don’t finalize on the presentation of the sermon until the sermon is actually being preached. Such an approach I find to be problematic in that it can easily degenerate into a pointless presentation.
The other type of preacher who uses this method has thought through a part of the sermon. Perhaps they have the big idea of the sermon. Then they let the sermon proceed without planning, but they do have the big idea of the sermon.
One thing that preachers should recognize is that whatever method of preaching without notes you use, you will have much preparation. At first your preparation will be just as extensive as when you prepared a full manuscript.