If your brother sins against you, go and show him his fault, just between the two of you. If he listens to you, you have won your brother over. Matthew 18:15
Christians tend to be too nice, skirting conflict. However, Jesus teaches that healthy conflict is necessary for relational and spiritual growth. It is required to keep clean accounts with others and stay focused on Kingdom priorities. Conflict resolution may be uncomfortable, but if an issue or offense is ignored it can become ugly, even explosive. Conflict resolution requires cooperation from at least two parties. There are two roles in the beginning stages of conflict resolution. One role is the confronter, the other role is the receiver.
If you are the confronter, it is critical to communicate the facts of the situation. If you are loose with the truth and cavalier in your confrontation, the situation will worsen. You probably need to have the details documented and verified. The second critical aspect of the confronter is the spirit in which he directs the conversation. Do not use an accusatory tone of voice. You are there in a spirit of reconciliation and healing. Avoid a condescending attitude, as you are a candidate for the same concerns you are bringing to your friend. Confront in a spirit of humility and grace, with the truth, in love.
The receiver, on the other hand, needs to beware of defensiveness, denial, and defiance. When confronted, the receiver needs to listen carefully and avoid interrupting with petty excuses. After hearing the accuser, the receiver can correct any misconceptions and inaccuracies. His spirit of correction is mature and levelheaded. Moreover, in most cases the receiver needs to apologize. Nine out of ten times a sincere apology from the one receiving the rebuke remedies the situation. On the other hand, a combative environment will just escalate the debate into a stalemate. Then nobody wins.