Selected quotes from an excellent article by Marianne Meye Thompson:
To preach the gospel is to proclaim the accounts of the Scriptures in light of the fact that their central character is God, and that the gospel is from God and about the God who is Father, Son, and Spirit.
It is so easy to make the most powerful of Gospel stories center on human action and not on God, to think that somehow our actions, our decisions, are the heart and center of the gospel story. To make that move is to sell out the gospel.
To be guided by the gospel is to remember that the gospel is first and foremost about what God does, and not about what we do.
Preaching should help people locate themselves in the context of the biblical story of God's creation of the world, call of Israel, sending of Jesus Christ, and promised consummation, because it is there that we find our identity and purpose. Preaching helps people to identify their stories with and submit them to God's grand story as found in the Bible; to find their identity, meaning, and hope in the purposes of God. Preaching narrates our individual, particular lives into the grand narrative of God's purposes and work in the world. Often, however, our stories get the banner headlines, whereas God's story is delegated to small print on the fifth page. It ought to be the other way around: God's story deserves the banner headline; our little stories deserve far less space.
Presbyterian theologian John Leith once wrote a book subtitled What the Church Has to Say That No One Else Can Say. This subtitle is an obvious pun: the church has as its gift something to say; but the church has that something as its responsibility or obligation as well. Advice columns can advise people about their problems; therapists can help us in our relationships; but the church can help people to situate their stories in the biblical narrative in a way that illumines their meaning. The church can and must speak the gospel. That is to say, the church articulates what it means that we live in a world created by God, tainted and marred in every way by sin, and straining for redemption.
Preaching helps people to understand this story, this "gospel of God," and to see their own stories as part of the larger story that begins with God's action and longs for the time when "God will be all in all."