There are two levels in Sermon Preparation namely: (1) the man-level and (2) the God-level as revealed in the first sermons of Jesus Christ and the first sermon of Apostle Peter. The Seven Spiritual Keys of an Effective Sermon in the textbook should train you well to know what a good sermon is, how to prepare an effective sermon, what signs to read during sermon delivery, how to correctly interpret them, and so on and so forth.
The Seven Spiritual Keys of an Effective Sermon are replicated four times in the Bible, one with Jesus Christ, two with Apostle Peter and one with Apostle Paul, so that by means of two or three witnesses in the Scriptures, this training and education that I am giving you will be established.
When you are preparing sermons on general Bible themes and topics outside Salvation, then use the Perfect Harmony Theory for Bible Translation, Interpretation, and Bible Teaching at chapter 2. For sermon preparation on the most important topic of Salvation, use chapters 19 to 24 where I have demonstrated the functionality of the Seven Spiritual Keys of an Effective Sermon.