Don't go into battle unprepared. Every preacher and elder owes it to himself and his congregation to inform himself of the issues at hand; who the leaders of the change movement are and a proper biblical response to their assertions. Preparation should begin immediately, "Put on the whole armor of God, that ye may be able to stand against the wiles of the devil" (Eph. 6:10).

Inoculate your sheep ahead of time so the virus of apostasy cannot invade them.  Don't wait until the error has raised its head among you and then try to warn folks against it.  By that time the damage will have been done and some will surely be lost...or you may be driven out. Thus did Paul (Acts 20:28-31).

Don't allow the enemy's agents in to do their subversive work in your congregation.  You are under no obligation to open your pulpit or classes to those who would  harm the church.  Let them know up front that they are unwelcome in your midst and that they will be given no opportunity to spread their views (II John 10-11).

Never make the mistake of assuming the proposals of the change agents are innocent and harmless. While one suggestion may seem innocuous in itself, it is but the nose of the camel in your tent. One by one, demands will be made until the congregation is overwhelmed and swallowed up in an accumulation of error.

Don't try to defend our flaws and failures.  The agents of change nearly always preface their proposals by pointing out some failure among our brethren. Of course we have failed to measure up to the perfect standard of Christ.  So have the change agents (Rom. 3:23). Gladly admit those legitimate charges and go to the heart of the matter; their desire to change the faith and practice of the church to a new non-biblical kind of religion.

Don't defend a tradition as a divine essential.  The enemy often points to some of our practices that are traditional ways of doing things and tries to justify his program of changes. Traditions of men that make void the word of God are wrong (Matt. 15:6-9).  Traditions of the apostles are righteous and should be observed (II Thess. 3:6).  Some traditions are harmless, such as the time of our assemblies, the length of them, the hymnals we choose, the kind of buildings we build. Never try to defend such things as divine obligations. Their proposed changes are clearly traditions of

Be totally honest with those whom you must challenge.  In the heat of combat it is easy to exaggerate the failures of your enemies or to distort their teaching to your advantage; or to deny your own shortcomings or mistakes. Perceptive people will see the slightest hint of dishonesty. 
Often they will give the change agents a free pass to do their mischief because they were misrepresented by a preacher or elder who opposed them.  Don't give them that advantage.

Never resort to vicious, unchristian personal attacks against the promoters of error.  Let the Spirit-given Word of Christ convict them (John 16:8-9). 
Let the facts of the case paint them as the heretics they are. Resorting to harsh, hateful attacks will cost you credibility with those whom you are trying to save.  Speak the truth in love (Eph. 4:15).

Don't compromise with the enemy. When change agents realize that they are not yet able to capture a congregation, they will propose a compromise.  They push for having an alternative service so that the stubborn traditionalists can worship in the same old tired way, and the enlightened ones can have a super-service that will meet their felt needs without hindrance and limitations. It is only time before the gangrene spreads and divisions does its destructive work.

Don't trespass upon the autonomy of other congregations. God created his church so that each band of Christians is independent and answers only to him. This has numerous advantages but also the limitation of allowing a church that so wishes, to embrace error and practice it. Autonomy means they have the right to do that and then answer to God for the mistake they have made.  Often in our zeal to protect the church, we are tempted to meddle in the affairs of another congregation of which we are not members.  Resist this temptation (I Pet. 4:15).

Don't walk away from the battle. In every war there are some soldiers, who because of cowardice, or weariness, or because the battle is not progressing as they wish, will abandon their position, leaving it to the enemy. We see this in some of our Christian soldiers.  The agents of change have no right to invade your congregation. They have no right to the hearts and minds of the flock. They have no right to claim for their use, church buildings others, who did not share their perverse views, built and paid for. Let them do the leaving. Hold Your ground. "Be ye steadfast, unmoveable...forasmuch as ye know that your labor is not vain in the Lord" (I Cor. 15:58).