John Wesley would train up those who thought they were called to preach the Gospel. He would teach them, train them and then send them out. When they came back he would ask them two questions: “Did anyone get saved?”
If they answered yes, he would keep them in his ministry. If they answered no, he would ask them another question:
“Did anyone get mad?”
If they answered no to this question he would tell them, “You are not called to the ministry!”
-Thanks to Pastor Doug Levy for this.