On preaching preparation

Certainly the preacher should prepare. 

He (or she) should prepare himself. He should pray. 

He should prepare his material. He should study God and his gospel, and the texts, and his people. He should know the big idea(s) and the aim(s) of his sermon.

Should he prepare his manuscript? 

And if he does should he read it out?

If you write a dull text and read it dully that's a double disaster. 

For some, there will be a great gain from in the moment spontaneous natural communication. 

For some, there will be great gain from the telling well contructed headings and phrases over which you sweated. Preparation may allow for conscion, and light and shade. 

Perhaps the ideal is some kind of half way house:

Prepare your material, but also prepare some of your matter or manner of delivery. 

Know how you will begin and end. 

Have some things that you will put pithily. 

Have that word play or alliteration, sometimes. 

What are your main points and how do you go from one to another?

Maybe even write a full manuscript, but try not to have to read it.  

What would your sermon look like on one usable page of A4? It might be a useful test as well as a help to delivery.