Much could be said about what makes a good sermon. It certainly should be engaging. It should apply to hearers' lives. However, there are two characteristics that are essential. They separate a preaching win from a homiletical failure. Faithful sermons must be expositional and must proclaim the gospel.
Expositional sermons expose the meaning of the text. As Mark Dever explains it, they take the points of the sermon from the points of the passage. Rather than starting preparation with an idea and then finding passages to support it, an expositional preacher starts with a text and digs for the Spirit-inspired, author-intended meaning. That meaning is then explained and applied to God's people.
This method places both the preacher and the congregation under the authority of the Scriptures. Although this is not the only way to preach expositionally, it generally works best to work verse-by-verse through books of the Bible. That way verses are handled in context. Hobby horses can't be exploited. Hard passages can't be avoided. Karis Church practices expositional preaching. We train our preachers in this method. We're not the only church that does it this way. But be sure to find one that does - that is, if you want to be shaped by God's holy word.