What are you inviting people to join when inviting them to lead/serve in your church? Possibly one of the best pieces of advice from my own experience is to invite people to serve for a season (specific period) at a time. When we do this it provides a natural time of recommitment and refocus for our servant teams. This also enables us to journey with those serving with us in intentional ways.
Here's an article from 2012 about how to find and develop leaders in your faith communities.