'You do it like this.

Did you ever play a game of forfeits called "When is it?
where is it?
what is it ?"' 'No, never.' 'Ah, that's a pity, because writing a sermon is very much like playing that game.

You take the text.

You think, why is it?
what is it?
and so on.

You put that down under "Generally." Then you proceed to the First, Secondly, and Thirdly.