The unfortunate fact is that many pastoral searches do not lead to a good marriage between the senior pastor and the congregation. I have watched great search processes and really poor ones. Here are some very practical suggestions that go beyond the need for prayer and the Holy Spirit's leading. They go to the core of understanding if this is likely to be a good fit or not.
Rather than a job description which no pastor can usually fill focus on the necessary competencies needed for the job. Then, write the actual job description around the individual you call with a focus on their particular strengths. He can then build a team to compensate for his weaknesses.
Resolve issues you know to be dysfunctional before you call a new leader - or - be fully disclosing as to what those issues are and how you will work with him to resolve them. Never hide the truth of your situation, just as you do not want the candidate to hide the truth of who they are. Give them the good, bad and the ugly so there are no surprises when they come. If the bad and the ugly scare them off, you have the wrong individual.
Ensure that your candidate knows where the authority lies in the congregation. It is a bad surprise for a new pastor to find out that authority he thought he had is withheld or that there are power factions in the church that hold veto power even over the board's decisions. If there is a church boss or some power faction, be sure they know about it.
Ensure that you are clear with the candidate as to what their authority is and is not. We don't like to talk about these things when we are courting a pastor but the fact is that they must know the boundaries of their role. If those boundaries are not acceptable to them they can self select out on the front end rather than fighting battles once they get there.
Every congregation has a DNA - some good and some problematic. Be sure that your candidate understands what that DNA is, what the strengths and weaknesses of the congregation as a whole are. If there have been significant conflicts or there are yet unresolved issues or a need for reconciliation tell the candidate.
The one group that the pastor must deal with regularly is the board. Be honest about the health of the board and allow the candidate to speak frankly and confidentially with whatever board member(s) they choose to get the real story. Unhealthy boards are as dangerous as unhealthy pastors. Don't hide reality from the individual who must deal with that reality for their leadership tenure.
Clarify in writing issues that need to be clarified in either direction. For instance, one search committee I met with could not explain who actually had authority for what: Board, senior pastor, staff or congregation. That is enough ambiguity to sink the relationship fast if not clarified. Some things need to be clarified up front just as in a marriage.
Don't try to make everyone feel good in this process. Good marriages take hard conversations and so do good pastoral/board relationships. Allow your candidate to ask the same hard questions of you that you ask of them. This is not about everyone being able to sing Kumbaya but about the ability to work together long term. Some things may need to be negotiated and agreed to up front.
Be clear about whether the new senior leader has the ability to change his leadership team which means staff. If you as a board see some staff as off limits for change (they are your friends or whatever the case) be honest about that.
Be honest, candid, up front, frank, how many ways can we say it! Tell the truth, don't gloss and be sure you are ready to keep promises that you make.
One of the fundamental ways that trust is broken early between new pastors and boards is when they are surprised by realities that the board fully knew but chose not to tell them in the candidating stage as it might scare them off. Where this happens the process lacks integrity and the potential damage to the congregation and pastor can be high. Be up front on the front end and you will build trust for the back end.