"AND HE WILL TURN many of the children of Israel TO THE LORD THEIR GOD."
Luke 1:16 (NKJV)
We could see the ministry or assignment of John the Baptist in this passage of the Bible: "HE WILL TURN MANY OF THE CHILDREN OF ISRAEL TO THE LORD THEIR GOD" (Luke 1:16 NKJV). He would also make ready the people prepared for the Lord (Luke 1:17).
Whoever is called into ministry work should endeavour to get to know what exactly God does want him or her to do; what to preach or teach, where to do the work, and the people he or she is assigned (Acts 22:21; Galatians 2:7-9).
We could see here that the assignment of John the Baptist is mainly to the children of Israel, to turn them to God, and make them prepared for the coming of the Lord (Luke 1:16,17).
If this important aspect of ministry work is not settled, as someone who claims to have God's call on his or her life; success in the ministry work would be a mirage or an illusion.
Although, the details of what you are called to do might not be fully known at the onset, but you have to know what to start with: what to do, where to do it, how to do it, and when to do it—the commencement of the work.
If you move ahead of God without getting some of these basic things settled, you may find yourself toiling in the work without any significant progress.
Note: getting to know these basic things is through strong intimacy with God. They are not usually sent through another person. They would be known through your communion or fellowship with God. They are the things that you get to know in the atmosphere of Father-son relationship.
If the cordiality is there in your relationship with God, they would be made known to you through inward witnesses—they come as thoughts. God usually would paint the pictures of whatever He wanted you to do in your heart.
Peace.