Sometimes it helps to just listen and not say anything and ask questions that help them think it through . since it is God that does the good stuff through us . generally helping them remember God and how good He is can't hurt .
“If another member of the church sins against you, go and point out the fault when the two of you are alone. If the member listens to you, you have regained that one. But if you are not listened to, take one or two others along with you, so that every word may be confirmed by the evidence of two or three witnesses. If the member refuses to listen to them, tell it to the church; and if the offender refuses to listen even to the church, let such a one be to you as a Gentile and a tax collector."
We should let our brothers and sister know when they do something wrong. Encourage them to take it to God and confess the sin to God. Let them know that God loves them and that He will forgive them of whatever they've done. Then, it also helps to be a good example.
In Matthew 18: 15-19, Jesus gives his disciples a set of steps for dealing with a brother or sister in Christ who has sinned against you. I'm not posting the whole thing here; I'll summarize:
1. Approach him in love and meekness privately. If he won't apologize, 2. Go back to him with a couple of Christians as witnesses, and if he still won't listen to you, 3. Take him before the congregation of the church. If he still refuses to listen to you, ten treat him as you would a pagan or tax collector. GOTCHA is the word. Because at the beginning of this chapter, the disciples ask him who will be greatest in heaven. After a sound and divine answer; children, they should have stopped talking. But next, they wanted to know what to do when another believer wrongs them. The last thing he says is the clincher, "treat them like pagans and tax coll." Jesus was always with pagans and tax collectors, eating at their homes, attending their weddings and such, and visiting with them. He treated them with kindness and dignity, healed them, fed them, delivered them, raised them from the dead, and ultimately gave his life for them.
I wonder how often Jesus was left with nothing to do but roll his eyes.