Contacting the Session
The process of becoming a minister of the gospel begins (so to speak) when a man speaks to his session about his being called to the ministry. Or it may begin when an elder or elders speak to him about the possibility he might be called. Every minister's story is different, but the process begins with such a conversation.
What does it mean to be called to the ministry? Usually in the Reformed world we speak of an internal call and an external call. The internal call is the candidate's intense desire to become a minister. The external call has two parts. First there is recognition by the church (the wider church) of the candidate's giftedness and suitablity to the work of ministry. Secondly a call is extended to the candidate for service as a minister.
It is important for men to speak to their elders about the ministry. There are many weighty questions a young man may have about the ministry, that his elders may be able to answer not only with the benefit of their experience, but also with their knowledge of the man himself.
It is also important for elders to speak to young men about the ministry. There is a pressing need for new ministers in the church. Who is more suited to identify men with the gifts for future ministry, than the elders of the church? "The harvest is plentiful, but the laborers are few. Therefore pray earnestly to the Lord of the harvest to send out laborers into his harvest." (Luke 10:2)
Pastoral Rule by Gregory the Great
Guide and Expectations for Coming Under Care