Tabletalk Magazine‘s interview with John Piper about those who feel they are called to the ministry:
A true divine call to the ministry (in general, not to a specific place or task) has at least four components, with very rare exceptions.
First, it involves a recurring and increasingly compelling desire for the work, in spite of fears and doubts (1 Tim. 3:1). The desire is more than a one-night flare-up at a high-spirited meeting. It endures through changes.
It involves gifting from the Lord. An elder is to be “apt to teach” (1 Tim. 3:2). A perceived call without evidence of God’s equipping for the call needs more testing.
God’s call is perceived and confirmed by others in the fruitfulness of a person’s ministry. If God is calling you, He will incline you to humbly do whatever you can in ministry. People will see this passion and the good that comes from it. That will lead to confirmation and encouragement to do more. If spiritual people do not perceive your ministry as bearing spiritual fruit in others (faith, hope, love), it is doubtful that God has prepared you at this time for ministry.
Sooner or later, God opens a door for service in a life of ministry. It may not be the one you dreamed. When I was twenty-eight years old, I had finished formal education and had a wife and a child. One door of ministry opened to me. I took it as God’s gift and confirmation. I had never dreamed of teaching at Bethel College. It was a gift. And it was the next step in my call to the Word.