If one were to study church history, they would find out that as the last eyewitnesses of our Lord died off, false doctrine and false teachers went up.
The devil can't stand against strong leadership, so he waits until they die off or lose their influence.
Act 20:29 For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock.
Act 20:30 Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them.
Act 20:31 Therefore watch, and remember, that by the space of three years I ceased not to warn every one night and day with tears.
Paul was aware of this and so are other strong leaders and will not cease to warn others so that they can be prepared. We are not ignorant of his devices.
As false doctrines and teachers abounded, there must be a way to tell who is false and who is not. Probably during that time, much of that was done by reputation and/or who they studied under, assuming that what they were taught by their teachers was what they themselves still believed and clung to. A good name is rather to be chosen than great riches. Another way was by what doctrine they held to. Jesus and Paul were all concerned about feeding His sheep so that they would know truth so that if someone came around teaching something different, they would be ashamed.
Nowadays, there are many oneness organizations that hold to the basic doctrines of belief in one God,
Acts 2:38 salvation, Jesus Name baptism for the remission of sins, baptism of the Holy Ghost, and holiness.
If a traveling evangelist made himself available to a local church, probably that Pastor would ask for references - which speaks to his reputation and having a good name - and what basic doctrines he holds to. I can't imagine a 3 stepper
Acts 2:38 church allowing a 1 stepper evangelist to come preach to some possible sinner, never been-born again people in his congregation.
So reputation and basic doctrines and holiness is probably what certain pastors look for nowadays in determining whether to let a traveling evangelist that they haven't heard of before, stand behind his pulpit.
Organizations can be a way of guaranteeing basic doctrines and some type of minimal agreed upon set of holiness standards. However, references would probably still need to be checked out to ensure that just because they believed in certain basic doctrines and minimal holiness at one point in time in the distant past, doesn't necessarily mean they still hold to those things now. While, yearly re-affirming a commitment to doctrine and holiness could be one way to ensure that, as we have seen in at least one organization, signing a person's name to re-affirm beliefs in basic doctrines and a minimal holiness standards doesn't mean anything to some. But perhaps a long time ago, if one held a "current" license with a certain organization, it would give some comfort in not having to do as much checking.
From Frank Bartleman's Azusa Street...
"A high standard was held up for a clean life. 'When the enemy shall come in like a flood, the Spirit of the Lord shall lift up a standard against him" (
Isa. 59:19)" - page 54