Answer:
"Pastor" -- if he's a pastor; if not, "Reverend" is normally the title used.
In Australia, "Reverend" is commonly used for Baptist pastors who have undergone extra study.
It is common for Baptist ministers to be called "reverend" but that is not a title that is found in the Bible that's used in reference to ministers. The word appears in the Bible (in the Old Testament) only one time, and it is describing God.
Psalms 111:1 (KJV): Praise ye the LORD. I will praise the LORD with my whole heart, in the assembly of the upright, and in the congregation. Verse 9: He sent redemption unto his people: he hath commanded his covenant for ever: holy and reverend is his name.
The more appropriate title would be "brother", "preacher", or "pastor" (if he is a pastor). These three titles are found in the New Testament and any of them are acceptable titles of address.
Acts 22:13 (KJV): Came unto me, and stood, and said unto me, Brother Saul, receive thy sight. And the same hour I looked up upon him.
1 Timothy 2:7 (KJV): Whereunto I am ordained a preacher, and an apostle, (I speak the truth in Christ, and lie not;) a teacher of the Gentiles in faith and verity.
Ephesians 4:11 (KJV): And he gave some, apostles; and some, prophets; and some, evangelists; and some, pastors and teachers;
The most common way Baptist ministers are addressed is "Brother." The word "Brother" is used in the Bible as a title of address, like the word "mister" is used. The word "preacher" and "pastor" are occupations.
By the way, the Bible also forbids the title of "father" for it is a reference to God himself, not man.
Matthew 23:9 (KJV): And call no man your father upon the earth: for one is your Father, which is in heaven.