RE: "seek to restore those caught in sin in a spirit of gentleness"

Details, please. How is this best done?
-- How can we best pray?
-- How can we best prepare for difficult conversation? What specific knowledge – Bible verses, other written guidance, statistics on cohabitation outcomes, etc. – would be good to be mindful of?
-- What do we do with the awareness of our own failings?
-- How can we best engage a believer?
-- How can we best engage a non-believer?
-- What kinds of rationalizations might we anticipate hearing, and how might we best respond to each?
-- When it appears from an initial conversation that a loved one has little interest in reconsidering his or her lifestyle, what then?
-- When it appears that a loved one is willing to reconsider his or her lifestyle, what then?
-- What can we learn from actual accounts of pastors and other Christians attempting "to restore those caught in sin"?
-- What can we learn from actual accounts of cohabiting couples who heeded Christian counsel and chose to live apart in preparation for marriage? How were they challenged? How were they blessed?