The Exiled Preacher has a post up on George Whitefield and Expository Preaching. Guy Davis, the author, writes about how difficult it can be to use a manuscript effectively. Certainly many of us have left our manuscript for a second to "riff" on a theme or go down a different direction. However upon attempting to come back to our manuscript we find it difficult to find the correct place. Because of this, Davis has spent the vast majority of his career as a preacher without using notes.

Time Needed

Davis notes that an extemporaneous sermon requires at least as much preparation as one that is read. The preacher must make sure that the sermon is structured well. Davis notes that this structure should be both "clear and straightforward."

What To Memorize

The preacher does not attempt to memorize the whole sermon. There are methods that seek to do that, but I think that the most effective ones memorize some sort of outline. For example Joseph Webb, in Preaching Without Notes presents an inductive outline that is held together by a controlling metaphor. Koller in How To Preach Without Notes provides a deductive outline with points and sub points. An interesting approach is Litchfield's in Visualizing the Sermon who suggests creating an outline of images. While I do think that preparing a full manuscript is helpful, for archival purposes as well as providing precision to word choice, having a clear outline is necessary for preaching without notes.