The Bible. A pastor’s first priority is to preach the Word (2 Tim. 4:2). A pastor-in-training’s first priority should be to study the Word.
Holiness. The primary qualifications for an elder are moral and spiritual (1 Tim. 3:2-7). A pastor is to shepherd his people by his own example (1 Pet. 5:3). Therefore a man pursuing the ministry must diligently seek after consistent, hard-fought holiness.
Humility. To shepherd God’s flock you must follow Jesus’ example in serving, rather than being served (Mk. 10:45). Humility must be a distinguishing mark of an under-shepherd of God’s sheep.
How to preach. Since preaching is the main work of a pastor, a pastor-in-training should seek every possible opportunity to preach. He should also solicit the criticism and advice of experienced pastors.
How to disciple. In order to be a pastor, a man should know how to personally instruct, encourage, counsel, comfort, and rebuke his fellow Christians. Not only that, but in order to even consider being a pastor he should have a track record of personally doing people spiritual good in these ways.
What the Bible says about the church. The apostle Paul says that when he came to Corinth, he laid a foundation like a skilled master builder (1 Cor. 3:10). In order to build wisely, a pastor must know what he’s building. Therefore a pastor-in-training must diligently study God’s own blueprints for the church which he’s given in his Word.
How to handle criticism, encouragement, and flattery. A pastor will receive all three. He needs to know how to humbly receive and profit from criticism, gratefully receive and profit from encouragement, and wisely deflect flattery.
Patience. Young men who are training for ministry don’t usually have an overabundance of patience. That’s a problem, because pastoral ministry requires it in spades. Pastors-in-training should pray for patience, cultivate patience, and learn from experienced pastors how to serve the same people day in and day out for decades.