How is a good study of a particular bible passage connected to good teaching on that bible passage?

Good teaching of the Bible flows from having a good understanding of the Bible.  So without first studying a particular Bible passage for oneself, in its context within the Bible, a teacher would not be well prepared to teach that biblical section.  

In studying the Bible, a teacher is also urged to keep the message of Christ central to all Bible teaching.  Jesus himself criticized the Pharisees for approaching the Bible in a way that studied it without seeing the message of Christ inherent it.  Jesus said to them, " You study the Scriptures diligently because you think that in them you have eternal life. These are the very Scriptures that testify about me, yet you refuse to come to me to have life" (John 5:39-40).