Nehemiah 8:8 (NIV)
They read from the Book of the Law of God, making it clear and giving the meaning so that the people could understand what was being read.
That is what expository preaching is, making God's word understandable and exposing the meaning of the text. I have been in churches where the minister, dressed in long flowing robes, stands in the pulpit and gives his sermon. I have heard sermons where scripture is never read or quoted and where Jesus Christ is mentioned. Oh, God might be mentioned, but mostly as an approver of social programs we ought to be doing.
An expositor of the word of God, never lacks for a subject and never lacks for the richest source material the world has ever known. When I teach a Bible Study, that is what the topic is, the Bible, what it says, what it means and how it applies to us personally. The approach I like to take is to pick a book of the Bible and start with chapter 1, verse 1 and work through the entire book, about a chapter a week. The nice thing about that approach is that you always know where you are headed next week, basically where you left off the week before.
Acts 20:27 (NKJV)
For I have not shunned to declare to you the whole counsel of God.
Romans 10:14 (NKJV)
How then shall they call on Him in whom they have not believed? And how shall they believe in Him of whom they have not heard? And how shall they hear without a preacher?