Philosophy of Preaching
Some Christians believe that preaching is "successful" if it is entertaining, or concise, or conveying truths by simple storytelling (rather than making the congregation think about some deep theological concept). But this perspective reveals what man wants preaching to be and not what God wants. The Bible paints a completely different perspective of preaching. One of the specific New Testament words used to describe preaching is "heralding." This is one-way communication in which the herald merely states what the king decrees. So the preacher is merely communicating what God has decreed (i.e. "Thus saith the Lord").
Other New Testament words used to describe preaching include reproving and rebuking (II Tim. 4:2), teaching and warning (Col. 1:28), reasoning and explaining (Acts 17:2-3), exhorting (Titus 2:15), and feeding (or shepherding, Acts 20:28). These words reveal a more serious approach to preaching -- not the simple, concise, entertaining model that man desires.
Preachers have employed several kinds of sermons throughout church history. Topical, textual, historical, expositional, and even devotional sermons have been used effectively. But it is the expositional sermon which clearly fulfills the Biblical idea of preaching. First, an exposition is the best way for a preacher to prove that what he is preaching is indeed from God (and not just his own thoughts). Second, an exposition is truly "reasoning and explaining" what God has said in a given passage. In addition, this expositional style can (and should) be used in textual and topical sermons. Third, as a preacher continues to preach expository sermons, he is actually showing (instructing) the congregation how to properly study a passage.
This brings up another point to consider. As the preacher develops his sermons, should he primarily focus on believers or unbelievers? I Corinthians 1:18 says, "The preaching of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God." Clearly, it is believers who appreciate the preaching of God's Word and benefit from its instruction. In addition, most churches refer to their services as "worship services." This also implies that believers are the primary focus of preaching. There are certain times when evangelistic sermons (preaching to unbelievers) are appropriate or necessary. But that ought to be the exception and not the rule.
Does this mean that visiting unbelievers will miss hearing the Gospel? No, not at all. Preachers often refer to incorporating a "redemptive element" into their sermons -- a portion of the Gospel that relates to the passage he is expounding. If there are visitors present, the preacher can then expand the redemptive element to include the whole plan of salvation, even though that might not be the primary point of the sermon. This can be accomplished quite easily in an expository sermon.