The Organization of the church
When we talk about the scriptural organization of the church of Christ, we need to understand that the churches of Christ (Romans 16;16) are local congregations who pattern themselves after the Holy Scriptures.  Those who are members of those congregations are a part of the body of Christ universal, over which He (Jesus), is the Head, and over which He has all authority.  Christ has given instructions regarding the organization of each local church or congregation.  There are to be men, known as elders, who oversee that local work.  Elders never had authority over another congregation. In the New Testament we see churches with a plurality of elders (Acts 14:23) over one congregation which they oversaw and tended.  
There is wisdom in God's plan because it has a system of checks and balances build in with a plurality of elders.  Bishop, pastor, shepherd, and overseer are all terms that also refer to an elder.  These men had to meet certain qualifications outlined in 1 Timothy 3:1-7 and Titus 1;5-9.  Preachers and ministers were never called by these names unless they were also qualified to serve as an elder. 
There are also deacons in the New Testament, but not a "board of deacons" that made decisions on spiritual matters.  Deacons in the New Testament served under men who were elders. Deacons too, had to meet certain qualifications as found in 1 Timothy 3:8-13.  
Preachers were never in charge of the church in the first century.  In God's pattern, preachers are to serve under the oversight of the elders.  They are not the leaders of the church in the sense of making the final decisions. Preachers are not elevated over the members and follow under the oversight of the elders who rule over them (Hebrews 13:17).  You will also notice when you visit a church of Christ, that the preacher never wears the name "reverend" or "father" or other religious title (Matthew 23:9, Psalm 119:9 KJV).  That is God's plan and it is one that we follow very strictly.  
Although there are many congregations of the churches of Christ throughout the world, each congregation is independent and self-governing, with Christ as our only Head.  We have no earthly headquarters, as this is brought out in the New Testament, and congregations are bound to each other only by their mutual adherence to the Bible as the sole rule of faith and practice in religion.