Don't badger or berate them for their beliefs!
Ask questions, engage in respectful conversation that isn't limited to the WTS!
Treat them as you would if you were still 'in' and they were 'friends'.
Remember that individual JWs hold differing opinions than WTS-partyline opinions, they only open up about them when they feel comfortable and safe.
Be the good Samaritan, practice the golden rule.
Don't go roaring like a lion, rather thread gentle as the lamb.
For those of you like to envoke Jesus' harsh 'viper' words......those words were spoken to Pharisees who at the time were playing theocratic strategy with Jesus........not the R&F!
Be a friend, not an enemy! We are all one human family after all!