Interestingly enough, I do not know of one church that does not have small groups in one form or another. Many of them do not have a declared small group ministry, but people will get into small groups regardless of whether or not small groups is an official ministry. People naturally and automatically seek out relationships. We do it automatically. It has been said that if someone who is new to the church does not form a relationship with someone else in the church within a few months, they are likely to leave the church or, at best, always be on the fringe of your church.
As you think about starting small groups, don not discount the natural small group relationships that already exist in your church. Part of creating Christian community is helping people to see that their existing relationships can revolve around the mission of the church. This, in turn, helps people use their routine, daily relational time with people for the glory of God.
That is what Jesus did. He did not necessarily try to organize a small group ministry. Instead, he started a relational ministry that functioned in small groups. He then modeled and taught what it means to live in relationship to God and to one another through His everyday life. Yes, Jesus participated in the Jewish Synagogue activities, but His ministry was in everyday life (John 15:15).
What does a Christ-centered small group do? The simple answer is that it lives in relationship to the Lord and to one another. God's Word dedicates a great deal of its content to this community. Consider the following passage:
"They joined with the other believers and devoted themselves to the apostles' teaching and fellowship, sharing in the Lord's Supper and in prayer. A deep sense of awe came over ...