Reverend (abbreviated "Rev."), a title of respect applied to clergy since the fifteenth century, has been used as a title prefix to clergy names since the seventeenth century. In some churches, such as the Episcopal church, the practice is to use "the Reverend Ms. Smith."
In many areas of the country, United Methodists refer to the pastor as "the preacher" or address him or her as "Preacher Smith." This is an anachronistic reference from the days when most clergy were circuit riders. Today, clergy are much more than preachers. Elders are ordained to service, word, sacrament and order; and deacons are ordained to service and word.
Calling a clergy person "pastor" is common in many parts of the United States, and this practice is increasing among United Methodists. In a Lutheran church setting, "pastor" is the prevailing term. "Pastor" comes from a word meaning "shepherd," and it is a strong and appropriate term.
In many churches in many areas of the country, church members still refer to their appointed pastor as "the minister." However, United Methodists are discouraged from using the term "minister" to describe clergy, since all members are ministers by virtue of their calling in baptism to share in "Christ's royal priesthood." To refer to the appointed clergy as "the minister" tends to reduce everyone else to the role of "listener," "consumer," or "recipient."
"Brother" is still used by some, but not much these days. The appellation, "Brother Smith" is anachronistic and colloquial. Theologically, it is a good term (Brother Smith or Sister Smith) for the relationships we have as sisters and brothers in Christ. However, it does not convey anything unique or distinctive about the role of the ordained person within the local church community or recognize his or her distinctive calling to Holy Orders.
In summary, "the Reverend" is a term of address that you would or could use in writing to clergy or in introducing them. "Pastor" is a more intimate term of relationship, and it may be used as a single word or in combination with the first or last name of the pastor. "Brother," "the Minister," and "Preacher" are regional terms and are, generally speaking, less appropriate.
For another article that explores the question of address of clergy, see "Are 'Mother' and 'Father' Appropriate Titles for Protestant Clergy?"