Be sensitive to the worldview and emotional wiring of non-Christians. Think in advance about how your sermon will sound to them.
When you arrive at a point in your sermon that you think would be particularly interesting or offensive to non-Christians, pause and explain it in greater detail.
When you do so, explicitly address non-Christians. You can say something like, “If you’re not a Christian, I wonder what you think about that last point…”
In your sermon, tell non-Christians that you’re glad they’ve attended. Encourage them to ask you and other church leaders questions after the sermon. If they came with Christian friends, encourage them to speak to them about the sermon.
Explicitly preach the gospel in every sermon. In every sermon explain to non-Christians how they can become Christians. Because all Scripture points to Christ (John 5:39), no text of Scripture has been fully explained until it has been related to the gospel.
Be willing to admit that Christians make mistakes; candidly acknowledge bad experiences that they might have had with Christians.