The Southern Baptist Convention (SBC) is the name of the denomination as well as the annual meeting where major policy decisions are made. It controls the six SBC seminaries, sends out missionaries overseas and within North America, controls a publishing entity called Lifeway Christian Resources, and controls a financial entity called GuideStone Financial Resources which provides health insurance, retirement plans, etc. for church staff members and SBC employees. The SBC has no direct authority over anything except its own operations which I have just summarized.
There are conventions in the states as well, e.g., Kentucky Baptist Convention. The state conventions have various operations from state to state, including Baptist colleges, hospitals, children’s homes and camps. They also provide hands on direction and supervision of SBC missionaries within their territories. The state conventions have no direct authority over anything except their own operations.
Southern Baptist churches form associations, usually composed of all the SBC churches in one or two counties. The association has the power to exclude any church that does not maintain doctrinal views consistent with their own. I have seen this power exercised on a couple of occasions.
Each church is ultimately in control of its own destiny. It is solely responsible for securing and supporting its pastor and staff. Each church owns its own property and no church property ever reverts back to any denominational entity. Each church has its own mechanism for accepting and expelling members. I have heard of members being expelled but have never seen this happen. Strangely, many SBC churches have no formal statement of faith. All creeds, including the Apostles Creed, are anathema to Baptists. Most Baptists prefer to go straight to the Bible on matters of faith and morals.
The SBC has a statement of faith called The Baptist Faith and Message: sbc.net/bfm/bfm2000.asp (I suggest you take a look at it–it’s an easy read). This has gone through several versions, the most recent one having been adopted at the annual convention in 2000. Many churches and several state conventions have adopted it but following it is not mandatory. A number of churches and state conventions that had adopted the earlier 1963 edition declined to adopt the 2000 edition because it takes strong stands on the husband being the head of the family and on women being ineligible to serve as pastors.
Having said all this, which is somewhat rambling and off point at places, anyone can be a member of a SBC church who makes a profession of faith in Jesus Christ, undergoes baptism by immersion, and asks to become a member. Southern Baptists are rather strict on matters of morals, although they have become a lot more liberal in recent years concerning divorce and remarriage. I guess they had to, otherwise they would not have anyone to occupy positions of leadership. However, they don’t pay a lot of attention to matters of doctrine. Each member can believe whatever he or she wants to, but those who stray too far off the ranch won’t be given positions of leadership in the church.