In no particular order, here are some reflections, musings, and bits of advice on the noble task of preaching the Word of God.
1. I've heard it attributed to Tim Keller that you have to preach at least 200 sermons to get good. (Or something like that.) I think this is generally true. For those gifted to preach, it does take a long time to hit your stride and become reliably good, and even then, you keep growing and refining. For those who aren't gifted to preach, I think even reaching the 200 mark shows no discernable growth. Someone is ungifted to preach when they've been at it a long time and show no real development. Sermon 201 is probably not noticeably improved from sermon 1.
2. I personally favor the use of manuscripts, but I understand they're not for everyone. If you can't preach from a manuscript without sounding like you are reading a manuscript, it's probably not for you.
3. When I started preaching, I used outlines (2-3 pages). I expected that as I got more experienced and confident in the pulpit, I would be taking less material. The opposite has proved true. The longer I go, the less I trust myself to speak without the train-track of my manuscript (usually 10-12 pages).
4. I don't think short messages are usually very good, but there's nothing worse than a sermon that is too long. Don't try to say everything. Do the text justice, proclaim the gospel, and don't feel the need to turn your weekly sermon into a conference talk. For most preachers, I suspect 30-40 minutes is probably the best range, but, again, a bad sermon can't be too short.
5. I believe that your devotional prep should take longer than your exegetical prep. Don't overcook your sermon, but don't pressure-cook your communion with God.
6. Thinking missionally, I think there is some truth to the admonition to "preach to who you want." But it's not for no reason Peter says to "shepherd the flock of God that is among you." Preaching to the congregation of your vision is often a great way to lose the congregation God in his wisdom has given you.
7. Work with the text on your own first, consult commentaries last. Always better to borrow than to steal.
8. I think topical sermons are fine so long as they're preached expositionally. ;-)
9. If Christ is as glorious as he says he is, making him the point of the sermon—no matter the text—makes the most sense.
10. Preach a biblical text. The only reason not to is if you think your ideas are better than God's.
11. A steady diet of "how-to" sermons doesn't make Christianity more accessible or relevant to people; it actually, over time, burdens them and makes them feel constantly on spiritual probation.
12. It takes some people all the faith they've got that week to get through the church doors on Sunday morning. Why would we want to offer them anything but good news and the comfort of Christ?
13. If the Bible is right when it says the gospel is the power of salvation—and it is—and if the Bible is right when it says it's only by beholding Christ's glory in the gospel that people can be transformed—and it is—it doesn't make sense to marginalize the gospel or save it for special occasions.
14. Preaching expositionally with the unity of the whole Bible in mind is a great way to make sure you're emphasizing both law and gospel according to their biblical proportions.
15. Obviously, if you're faithfully preaching God's Word, it doesn't really matter if you're preaching from a music stand, lectern, high-top table, or with no stand at all, but I personally do like a good old-fashioned wooden pulpit, because I like the way it reinforces the idea that God's word is solid, firm, "big," an anchor in the stormy seas of life. A good solid pulpit conveys aesthetically the authority and the firmness of God's Word. Again, no reason to be dogmatic about something so preferential, but maybe consider what your preaching environment communicates? Is your setup inadvertently communicating something flippant, casual about encountering the living God?
16. The sermon can serve as a biblical course of correction to pervasive disobedience in the church and a spur to repentance, but please don't use your sermon to passive-aggressively address problems (or problem people) in your congregation. No subtweet sermons.
17. I learned early on that homiletical rants directed at certain subgroups—young men, for instance, who need to "grow up" or whatever—tended to be ignored by those who most need to hear them and instead hurt the hearts of sensitive souls who don't necessarily need them. When I would yell Driscoll-like at young men especially, I learned that those in my crosshairs didn't think what I was preaching applied to them and that I was actually stepping all over men who were already working hard. This is immature preaching. There are better ways.
18. You can't make everybody happy. That's not the point of preaching, anyway. Don't preach as an employee of the church. Preach as a servant of God, accountable first and foremost to him.
19. Personal illustrations should mainly serve in the area of confession or self-deprecation. Always holding up yourself as a good example is a fantastic way to preach yourself instead of Christ crucified.
20. A simply good preacher who can look in the eyes of the flock beats a really great preacher on a video screen any day.
21. Passion, brother, passion. Give us your theology, yes. Don't short-shrift us on the text. Don't confuse yelling for preaching. That's not what I'm saying. Give us your rhetoric and your logic sure, but give it to us affectionately. "Preaching," as Martyn Lloyd-Jones put it, "is theology coming through a man who is on fire." (See also #5 above.)