1) Any excommunication will have substantially less support 2 years after it is administered.
As the anger dies down more general issues begin to be questioned and people will become more circumspect. Make sure you will still have sufficient support even if people explore the issue from a variety of angles.
One of the best ways to do this is to have a recorded vote of the majority affirming a specific statement (and allow for various statements), like what is done in superior courts. You want people on record agreeing to the statements and you want them to feel comfortable that the statement that they signed reflected their views at the time. It is not neccesary that the statements reflect their current view however.
Another key point is to convict on the underlying issue or not at all. It can be very tempting to go for an easy conviction with the major crime in mind (see link for a pastor recommending exactly this approach). In the example the pastor advocates excommunication for contumacy when the underlying issue is embezzlement. Do not take the cheap way out and go convict on a minor offense when the major offense is the real reason. The evidence for the major offense will disappear and often the minor offense information is fairly weak. Without the major offense the actions on the minor offense will seem excessive and will soon lack support.
2) Keep good records
Make sure you have good records, regarding the facts and the debate. Think about how much effort courts go to in maintaining records. Make sure that you have written records from everyone. So for example if you assert that person X did Y to Z have a deposition from Z confirming that fact, and have Z sign it. If you can't do that then have 2 witnesses to every charge and again have them signed.
If there was counter evidence presented at the time have excellent records as to how it was investigated and why it dismissed. The congregation will excuse leadership for making errors, they won't excuse leadership for not performing due diligence.
3) Avoiding bullying the membership.
Avoid things like bullying to get people to support leadership's position. Bullying of members will work in the short term and then fail in the long term. Members who reluctantly support will look for excuses to change sides as pressure increases. Leadership can easily get an excommunication motion through with 20-30% support. But they will need 65%+ support (and better yet 90%+) to defend it publically once the critique starts.
So, if the congregation is split on the appropriate penalty choose the lessor one.
4) Have a documented reconciliation / restoration process and keep it open.
Often excommunication is confused with anathema if the disciplining church is not seen as having a reasonable reconciliation option. Be sure that the level of repentance required is understood in advance and supported during. A congregation can split after the fact if the convicted offers an apology that some see as insufficient and others believe is sufficient. 3 types of apologies should be differentiated:
- A censure does not require repentance just to stand for it i.e. the person needs to acknowledge the censure and remain in obedience after its administration. They are not required to affirm the justice of the censure
- A call for repentance can be met via. a simple apology
- A demand for restitution requires actual fruits.
5) Have the extent of punishment or shunning be public.
Leadership should attempt to punish acts of cruelty perpetrated by members against former members, that your church does not approve of. Light censure of such acts is always seen as encouragement. Remember if you don't oppose it you encouraged it.
6) Have a genuine appeals process
It is important that the membership and outsiders believe the appeals process is genuine. Make sure the people involved in the appeals process were not the ones involved in the original conviction. If possible make sure that at least one appeal has been successful recently. The pre-existing appeals process will lower external criticism and will relieve pressure within the church. People who come to believe the original act was unjust or factually incorrect should be encouraged to enter into the appeals process. This helps separate dissent from division. There will always be a court of appeal, either the church will pick it or the public will.
7) Have a clear policy about what to do about old sins successfully covered up.
Either have a "statute of limitations" or indicate you excommunicating solely for the ongoing cover up. If there was no ongoing cover up then leave it be. People will be extremely angry about the cover up but anyone not lied to will think the anger is unjustified. These issues are very divisive.
8) Get a detailed written summary from the accused.
You want written statement of the accused's position on every specific acts and charges. There can be a great deal of disagreement about which facts were or were not confirmed after the fact. If you can get a confession even one with lots of clauses and justifications, get it.