The overwhelming majority of churches do not hurt people.
This link outlines some basic "warning signs" of a potentially unsafe group.
The more checks and balances that exist the safer you are.
A democratically elected church government with bylaws to protect its members, such as a church board that can discipline a pastor or if need be fire him.
Financial transparency through independently audited and annually published financial statements that disclose in detail all salaries, compensation and expenses of the church keep things open and honest.
Educational requirements for pastors that include college and seminary provides for a process that often produces more reliable pastors.
Denominational accountability provides another layer of safeguards.
Larger denominations such as the Southern Baptists, American Baptists, Church of the Nazarene, Evangelical Free Church and Assemblies of God, would be examples of churches that typically have these safeguards in place.
Most large Protestant denominations have such layers and provisions for accountability.