Sometimes as you continue to journey with the Lord, He will reveal something to you about someone.  First of all, test the spirit to make sure it is the Holy Spirit and not some divisive spirit just trying to stir things up.  Never forget that the enemy roams around just looking for a way to trip you up and eliminate you from your Kingdom assignment! 

Second, keep the information to yourself.  Do not share it with anyone else to include the person about whom you may have had this revelation.  Most often you are simply to pray for that person.