Here are some helpful posts on preaching:

6 Bullet Points on Preaching – Tim Challies
The Apostle Paul had a lot to say about preaching, but I think the majority of it can be grouped under six main headings or ideas. You could, of course, extract specific teaching points from each one, but I think there’s value in looking at them in a broad sense. Here is what Paul says about the preaching of God’s Word…

3 Questions To Ask of Your Sermon – Trevin Wax
The more I’ve thought about these questions, the more I am convinced that pastors ought to ask these questions of every sermon they preach. Teachers ought to ask these questions of every lesson they prepare. The questions are a helpful guide to keeping Christ as the focus of our ministry.

Preaching That Cuts to the Heart – Tim Keller (via Gospel Coalition)
Put another way, you should preach the truth, not just your opinion; you should preach the good news, not just good advice; and you should preach to make the truth real to the heart, not just clear to the mind.