Other than the obvious (believer's baptism) where do you think "Baptist" churches cease being Baptist (e.g., elder governance, satellite churches with no local church autonomy, etc.)?
1. Biblical Authority. Any church, regardless of the name on the sign, that does not accept the authority of the inspired, infallible written word of God is not Baptist.
2. Autonomy of the Local Church. Any church that is ruled from without is not a Baptist church.
3. Priesthood of the Believer. Any church that refuses to allow Priesthood of the Believer/Soul Liberty is not a Baptist church.
4. Two Ordinances. Any church that practices more than, or less than, two ordinances is not a Baptist church.
5. Individual Soul Liberty. See #3 above.
6. Saved, Baptized Church Membership. Any church that does not require every member to be both saved, by public profession of faith, and baptized, by immersion upon credible testimony of faith, is not a Baptist church.
7. Two Offices. Any church that has more, or less, than two offices is not a Baptist church.
8. Separation of Church and State. Any church that is an official State Church is not a Baptist church.