In the pagan world, when one person wrongs another, the first step is often to involve third parties: friends, a coworker, the boss, a lawyer, etc. In serious cases, the first step may be to take the offender to court. If either party is unsatisfied with the outcome of the court case, then the unsatisfied party can appeal to a higher court, and so on, until the Supreme Court gives a final ruling. In that system at its best, the goal is justice. For offenses among believers, however, Jesus instructs us in a different procedure and a different goal. In Matthew 18, Jesus establishes the pattern for a believer to follow when one of his Christian brothers has sinned against him. He says,
Moreover if your brother sins against you, go and tell him his fault between you and him alone. If he hears you, you have gained your brother. But if he will not hear, take with you one or two more, that “by the mouth of two or three witnesses every word may be established.” And if he refuses to hear them, tell it to the church. But if he refuses even to hear the church, let him be to you like a heathen and a tax collector.
The procedure seems clear enough. When some brother Christian offends you, there are four steps. We might think of these as a lower court, an appeals court, the (earthly) supreme court for Christian conflict resolution, and a final judgment. Read the rest here.
Full Contact Christianity 
Good lesson on these verses. Would like to see you expand the lesson through 18:20 to explain 18:20 in context as it is so often used inappropriately. Thank you for your work.