Cripplegate has some excellent quotes from preachers about preaching. The quotes support ten principles.
1. Effective ministry consists not of fads or gimicks, but of faithfully preaching the truth.
2. Preaching is a far more serious task than most preachers realize.
3. Faithfulness in the pulpit begins with the pursuit of personal holiness.
4. Powerful preaching flows from powerful prayer.
5. Passionate preaching starts with one’s passion for Christ.
6. The preacher is a herald, not an innovator.
7. The faithful preacher stays focused on what matters.
8. The preacher’s task is to make the text come alive for his hearers.
9. The preacher is to be Christ-exalting, not self-promoting.
10. Faithful preaching requires great personal discipline and sacrifice.
Read the whole post, including the quotations.