The first is children. When a couple begins to have children, they often begin to think about their children's spiritual development. Every parent wants to be able to talk about spiritual issues that inevitably come up with children. Yet another reason to have a healthy ministry to children and families.
Another motivation is change. When people move to a new city, they are often willing to integrate new pieces into their life, including church. Interestingly, this is one reason why new churches are often effective at welcoming previosly unchurched people. Folks are more willing to jump in when things are new, rather than coming into something established.
The third motivation is crisis. Crisis makes us re-evaluate priorities in life. When life moves into the realm of 'out-of-our-control' it is comforting to turn to a God is is never out of control. God has often used negative circumstances and times of crisis to help people wake up to spiritual realities.
These are all motivators in preparing someone to reconsider church. But they alone will rarely get someone to walk into church without an invitation from a friend. Always, always, always... the number one reason a person will walk into a church is because a friend they trust invited them. So be aware of these issues going on in the lives of your friends. It may be a good time to invite them to attend church with you!
