Gary Millar and Phil Campbell, Saving Eutychus: How to Preach God’s Word and Keep People Awake  (Kingsford NSW, Australia: Matthias Media, 2013), 50–61:

1. The more you say, the less people will remember. . . . “Biscuits and sermons are improved by shortening”. . . .
2. Make the ‘big idea’ shape everything you say. . . . That’s one of the best reasons to preach from a full script—you get to edit before you speak. . . . [From p. 64: “[I]t’s easier for your listeners to catch a baseball than a handful of sand.”]
3. Choose the shortest, most ordinary words you can. . . . The more complex your subject, the more helpful it is to describe it in ordinary words. . . .
4. Use shorter sentences. . . . This isn’t about ‘dumbing down’ your content. It’s about communicating complex content clearly. (But keep in mind that alliteration is no longer considered tasteful.) More importantly, it’s about sounding like a normal, conversational you. . . .
5. Forget everything your English teacher taught you. . . . [I]f you’re scripting a sermon you should expect it to read badly. It should break almost all the norms of good written expression and follow the rules of informal speech instead. . . .
6. Am I repeating myself? . . . [A]s you’re introducing a new idea, it’s incredibly helpful to restate the first sentence three times, rephrasing it each time but adding no new information. . . . Avoid giving too much information and learn the difference between the pace of your speech (in ‘words per minute’) and the pace of information (in ‘ideas per minute’).
7. Translate narratives into the present tense. . . . [This] makes a story seem real and immediate—it’s just like being there. . . .
8. The six-million-dollar secret of illustrating. . . . Don’t sweat over illustrating the complicated stuff—just illustrate the obvious! . . . Illustrate the obvious, and the complex ideas will take care of themselves, because your listeners will be fresh and focused enough to stay with you. . . .
9. People love to hear about people. . . . The journalist’s rule is this: if there are no people, there’s no story. . . .
10. Work towards your key text. . . . When you’re quoting a verse, help out the listener by setting it up before you read it, rather than after. . . .

[M]ost natural communicators—whether scripted or not—tend to do most of these things by instinct.

Related:

1. 8 Advantages of Heart-changing, Expository Preaching
2. Mike Bullmore’s 2008 Rom Lectures: “The Heart of Preaching and the Preacher’s Heart”
3. Tim Keller: Preaching to the Heart
4. Preaching Christ in a Postmodern World
5. Preach: Theology Meets Practice
6. Performer vs. Herald?
7. Just Preach the Point of the Text
8. The Best Part about Knowing the Biblical Languages