Pastors are communicators. We are charged with teaching and proclaiming life's most important message: the saving Word of the cross. As Paul said to Timothy, we are to "preach the word" (2 Tim. 4:2). Given this mandate, we should do everything we can to communicate in ways that really connect with people. We should want our sermons to stick.
A helpful book is Chip and Dan Heath's Made to Stick: Why Some Ideas Survive and Others Die, which explores six principles that make some ideas "sticky." While applying these principles is no substitute for powerful, Spirit-filled preaching and teaching, doing so could prove helpful in constructing sermons. According to these men, sticky ideas are characterized by:
- Stories 
Our sermons should be simple. This doesn't mean we should be shallow but that we should be clear. Paul actually made preaching with clarity a priority in prayer (Col. 4:4). Practically speaking, each of our messages should be about one thing. Homiletics textbooks call this the "big idea" or "central proposition."
In his great book on preaching, J. H. Jowett wrote,
"I have a conviction that no sermon is ready for preaching, not ready for writing out, until we can express its theme in a short, pregnant sentence as clear as a crystal. I find the getting of that sentence is the hardest, the most exacting, and the most fruitful labour in my study. To compel oneself to fashion that sentence, to dismiss every word that is vague, ragged, ambiguous, to think oneself through to a form of words which defines the theme with scrupulous exactness-this is surely one of the most vital and essential factors in the making of a sermon: and I do not think any sermon ought to be preached or even written, until that sentence has emerged, clear and lucid as a cloudless moon." 
Sometimes people listen to sermons the way airplane passengers listen to the flight attendant's announcements before takeoff. No one pays attention, because they've heard it all before.
Really smart flight attendants, however, occasionally arrest people's attention by changing their tone, incorporating humor, or being overly gregarious. While their basic message hasn't changed, their manner of conveying it has.
So it is with preaching. We are charged with proclaiming an important, life-and-death message; but most of our people have heard it before. That doesn't mean we should change the content, but perhaps we should adjust our manner. By changing our tone, speaking with urgency, choosing vivid words, and using fresh illustrations, we may arrest the congregation's attention.
Too much of our preaching is abstract. We outline our sermons with words like nature, purpose, and cause to define and describe biblical doctrines.
This is not all wrong; I've done it a fair bit myself. But if we don't move from the theoretical to the functional, from the abstract to the concrete, we're not likely to preach sermons that stick.
For example, which sermon outline do you think is most likely to help people?
1. The Source of the Corinthians' Gift
2. The Function of the Corinthians' Gift
3. The Purpose of the Corinthians' Gift
1. God gave each of you a gift.
2. God gave you them to use.
3. God gave them to use for the benefit of others. 
Another way to make sermons concrete is to use vivid imagery. This is partly why Jonathan Edwards' sermons were so effective. He didn't just talk about the justice of God's wrathful indignation against sin. He told sinners that
"The God that holds you over the pit of hell, much as one holds a spider, or some loathsome insect over the fire, abhors you, and is dreadfully provoked: his wrath towards you burns like fire; he looks upon you as worthy of nothing else, but to be cast into the fire; he is of purer eyes than to bear to have you in his sight; you are ten thousand times more abominable in his eyes, than the most hateful venomous serpent is in ours." 
Whether you like Edwards' rhetoric or not, the imagery sticks because he was vivid and concrete. "Abstraction makes it harder to understand an idea and to remember it . . . concreteness helps us avoid these problems." 
Our credibility comes first of all from God's Word. Since we claim to speak on God's behalf, we had better show that our words are clearly rooted in the text. As Bryan Chapell writes, "Scripture determines what expositors preach because they unfold what it says. The meaning of the passage is the message of the sermon. The text governs the preacher." 
But credibility also hangs on how we live. A dentist with crooked teeth would not inspire confidence; nor would an overweight nutritionist. So we must live faithfully by the Word we preach.
Puritan Richard Baxter warned preachers to
"Take heed to yourselves, lest your example contradict your doctrine, and lest you lay such stumbling-blocks before the blind, as may be the occasion of their ruin; lest you unsay with your lives, what you say with your tongue; and be the greatest hinderers of the success of your own labors." 
Finally, credibility depends on knowing the audience. It's one thing to exegete the text; it's another to exegete the audience. This is especially important when speaking to unbelievers.
Tim Keller, building on the work of Christian philosopher Alvin Plantinga, asserts that "people avoid Christianity not because they have really examined its teachings and found them wanting, but because their culture gives huge plausibility (by the media, through art, through the expertise and impressive credentials of its spokespersons) to believe a series of defeater beliefs that they know are true, and since they are true, Christianity can't be." 
Keller says that we must engage these defeater beliefs in our preaching and teaching. "The leading defeaters must be dealt with clearly and quickly but convincingly. Defeaters are dealt with when the person feels you have presented the objection to Christianity in a clearer and stronger way than they could have done it."  Doing so will give us enough credibility to persuade unbelievers to at least listen to what we're saying.
Sermons that stick also engage people's emotions. I don't mean that we should manipulate people or arouse "warm fuzzies" by telling lots of cute stories (although stories have their place). Nor do we want people to feel emotions that are not rooted in a clear comprehension of truth.
Jonathan Edwards was right when he said,
"I should think myself in the way of my duty to raise the affections of my hearers as high as possibly I can, provided that they are affected with nothing but truth, and with affections that are not disagreeable to the nature of what they are affected with." 
Of course, we can't really raise people's affections unless our own hearts are engaged. We must take truth so seriously that we are also profoundly affected by it.
No one has influenced my thinking on the importance of passionate preaching more than John Piper, who said, "What gives preaching its seriousness is that the mantle of the preacher is soaked with the blood of Jesus and singed with fire of hell. That's the mantle that turns mere talkers into preachers." 
Finally, sermons that stick utilize stories. It seems that most preachers err either in using too many or none at all. One pitfall of much so-called "expository preaching" is a dry, lecture-like style that neglects the imagination. These "all head, no heart" sermons were likened by Spurgeon to buildings without windows:
"A building without windows would be a prison rather than a house, for it would be quite dark, and no one would care to take it upon lease; and, in the same way, a discourse without a parable is prosy and dull, and involves a grievous weariness of the flesh." 
Spurgeon went on to fully develop this metaphor, teaching that:
- As windows let sunlight into a room, so illustrations illuminate a sermon;
- As a house must not have thick walls without openings, neither should a sermon be made up of all solid slabs of doctrine without windows of illustrations;
- As windows add to the design of a building, so the variety brought in by illustrations and stories enhances the design of the sermon;
- As open windows let in fresh air, "even so, an original figure, a noble image, a quaint comparison, a rich allegory, should open upon our hearers a breeze of happy thought . . . quickening their faculties to receive the truth";
- As a window that does not allow light (e.g., a window that has been plastered or boarded up) is distracting and ugly in a house, so an illustration that fails to illustrate a point is a distraction in a sermon;
- But that just as windows should not be too numerous (you don't want a glass house), neither should your sermon be all illustrations, with no truth; this is like setting a table with flowers--they may be pretty, but people will resent them if they are hungry for food. 
Bryan Chapell agrees: "I discovered while pastoring that the mind yearns for and needs the concrete in order to anchor the abstract.
"This does not mean that illustrations should be merely a cognitive crutch or a supplement to sound exposition. Rather, illustrations exegete Scripture in terms of the human condition, creating a whole-person understanding of God's Word. Illustrations are essential to effective exposition not merely because they easily stimulate interest but also because they expand and deepen understanding of a text. By grounding biblical truth in situations that people recognize, illustrations unite biblical truth with experience and, in so doing, make the Word more accessible, understandable, and real in ways that propositional statements alone cannot." 
It is also important to remember that the message we preach is itself a story-The Story, really-of our heavenly Father graciously rescuing our fallen world through His Son's death and His Spirit's power, resulting in a new creation called the kingdom of God. This is The Story we want to communicate, with Jesus as the Hero.Endnotes:
 Chip Heath and Dan Heath, Made to Stick: Why Some Ideas Survive and Others Die (New York, NY: Random House, 2007) 14-18.
 J. H. Jowett, The Preacher: His Life and Work (Harper & Bros, 1912) 133.
 Jay E. Adams, Preaching with Purpose: The Urgent Task of Homiletics (Grand Rapids, MI: Zondervan, 1982) 52.
 Jonathan Edwards, "Sinners in the Hands of an Angry God." Available online at http://www.ccel.org/ccel/edwards/sermons.sinners.html
 Made to Stick, 100.
 Bryan Chapell, Christ-Centered Preaching: Redeeming the Expository Sermon, Second Edition (Grand Rapids, MI: Baker Academic, 2005) 32.
 Richard Baxter, The Reformed Pastor (Edinburgh: Banner of Truth Trust, 1974) 63.
 Timothy J. Keller, "Deconstructing Defeater Beliefs: Leading the Secular to Christ." Available online at http://www.redeemer2.com/themovement/issues/2004/oct/deconstructing.html.
 Jonathan Edwards, Some Thoughts Concerning the Revival, in The Works of Jonathan Edwards, vol. 4, ed. C. Goen (New Haven, Conn.: Yale University Press, 1972) 387.
 John Piper, "Why Expositional Preaching Is Particularly Glorifying to God" (Louisville, KY: Together for the Gospel Conference, 2006). Both the transcript and the audio of this message are available online at: http://www.desiringgod.org/ResourceLibrary/ConferenceMessages/ByDate/1756_Why_Expositional_Preaching_is_Particularly_Glorifying_to_God/
 C. H. Spurgeon, Lectures to My Students (Pasadena: Pilgrim Publications, 1990 reprint, Four Volumes in One) 3:2.
 Spurgeon, 3:1-14. These thoughts are gleaned from just the first of seven lectures on illustrations in Spurgeon's third series of lectures to the students of his pastor's college, entitled The Art of Illustration.
 Chapell, 178.