When many smaller churches think of reaching new people they often focus on how they can get people to visit their churches on Sunday morning. That is trying to get people to come into a church through the front door. There is nothing wrong with that, but it is too limiting. Along with a front door strategy churches also need to consider how they can get people to come through the side doors. You'll notice that when I talk about the front door I use the singular term, and when I talk about the side doors I'm using the plural. The front door is primarily limited to one event, the Sunday morning service, that people might be attracted to, but the side doors can be muliple opportunities through which people can become involved in the life of your church.
Side doors are often the activities that your church is involved in outside the confines of your building. For example, your church may have a food pantry that makes food available to persons who need assistance. It may be that you could not only assist a family with food but you could also invite members of that family to assist you by serving in that pantry and give them an opportunity to meet the persons from your church who minister in that pantry. Through the relationships you would build they may be interested in finding out more about your church and begin attending the services.
Another side door might be something related to sports. A member of your church may coach a summer baseball team and be able to build relationships with the player's families. In those relationships it is likely there will be opportunities to share discussions about spiritual matters. I know one church that started a group for persons in the community who enjoyed bass fishing. A member of the church who fishes bass tournaments led this group and taught them some of his techniques. The intent was to reach unchurched persons who would enjoy being a part of this affinity group and to build relationships with these persons. A few years ago I was told of one megachurch that had over 200 such groups meeting in their church facilities each week. It has proven to be a very effective way to build relationships with unchurched persons and earn the right to talk to them about spiritual matters. There may be some persons in your congregation who enjoy quilting and would want to begin a group that would be attractive to other quilters. Some of those persons might be unchurched persons in your community who would enter into relationships with the quilters in your congregation. The side doors for your church is only limited by the number of things people in your church are passionate about and how many of them are willing to use that passion to build bridges to the unchurched in your community.
People who would be resistant to entering your church through the front door may have no problem being part of a group within your church when that group is focused on things that interest them. As they find the leaders of these groups to be people who are genuine, relational, and equally interested in the same things they are they will become more likely to be interested in learning more about your church. I should give a word of warning here. If they sense that this group or leader is only interested in putting another notch on his or her spiritual gun they will leave and never return.
Another thing to consider is that it's not necessary to have church members lead this group. If an affinity group was going to meet in our church I would want members of our congregation be part of that group, but that doesn't mean that only members could lead it. It could be a positive thing if non-members led some of these groups, especially if they brought a level of excellence to the activity. By having church members as part of the group the church would continue to have a connection with the other participants in the group, and they could ensure that whatever ground rules had been developed for these groups were followed.
I encourage you to sit down and make a list of how many side doors there are into your church. The next time you meet with your church leaders ask them to made a similar list and then begin discussing what other side doors might be possible in your congregation.