The saints are to be trained to share the message of Christ with their friends and family. The best use of social media is to connect with your friends and family and encourage them to join the church.
There are many ways to share your testimony. One church I know of that has a special class that teaches its members how to do this. After the class, those who attended were given the opportunity to videotape their testimony and then upload it to YouTube.
Even if you don’t want to market a new ministry opportunity, encouraging your church members to share it on social media is a great way to get people to “like” your page.
This method is much better than having the staff members of the church promote a specific ministry using social media. It is also better for them to create their own content and promote it in various ways!