The last thing you must do to prepare well for the transition while in seminary is to make a list: who will your mentors be in ministry?
You will inevitably face circumstances that you won't know how to handle, or will need some basic orientation for. Your first wedding or funeral; the first time you do a hospital visitation; the first Session meeting you moderate or Board meeting you oversee. You may not know how to lead worship effectively, or how to lead another through basic discipleship. There will be a thousand blind spots, things you didn't know that you didn't know-- until you were in the midst of needing to know!
You will have questions. How do you start to counsel one of your parishioners? How do you stop counseling without leaving them feeling abandoned? Are you spending too much time (or too little) preparing your sermon or lessons, or too little time (or too much) meeting with your congregants? Which issues are worth fighting for? How do you repent well when you've sinned against one of your members? What do you do about the strange situation that you never saw coming? Are you pushing for change too fast?
Where will you turn for answers to your questions? Where will you go for advice about your blind spots? You will serve yourself well if you've thought through who you will call or meet with in these times of need.
There will inevitably be some that you can't list at this point. Perhaps you will work under a seasoned Senior Pastor, or there will be experienced Elders and/or Deacons in your congregation who can guide you in the moment. There will certainly be other pastors around-- perhaps in your presbytery, or other like gathering-- and some of these will present themselves as available for such advice. Maybe, as it was in my case, there will be willingness in the man who put you in contact with your new congregation, and he will offer his wisdom and experience when you need it.
But even these present gaps that need to be filled elsewhere. In the midst of a funeral, your Elders and Deacons won't be as available for guidance; they will assume that you know what to do-- not just preaching the sermon, but ordering the service, guiding the family through their grief, leading the church in serving the bereaved. When you have conflict with your Senior Pastor, you will probably want to avoid talking to anyone close to the situation. There will be times when you need your mentors to know you, not just ministry in general.
Seek out, therefore, a few trusted mentors-- men who know you, whose experience and wisdom in ministry is trustworthy, in whom you know you can safely place your confidence-- and approach them. Simply ask them if they would mind if you called them from time to time when you need advice on pastoral ministry. I would be astonished if they refused.
It will be a lot easier knowing now than waiting until the first incident presents itself. Go ahead: get out a sheet of paper and make a list (maybe five names?) and begin asking these friends for their willingness. When you call them on the way to the hospital or as you wait for your first counseling appointment, you'll be so glad you did this now.