Through Paul, the Holy Spirit commands that we speak the truth in love. This command does not come to ordinary human beings, but comes with the context of the previous text which reminds us that we are supernaturally empowered to do so by way of the gifts that the Holy Spirit has given each believer in Christ.
The first thing we see is that we must speak. We must integrate our testimony into normal interactions with people, who if they choose to remain our friends and associates, will come to expect that this is part and parcel of who we are. In this lifestyle, when confronted with erroneous thinking, we most likely will repeat something the other person has already heard us say. Or at the least, a line of dialogue consistent with our character, which, if expected, is less likely to be taken offensively.
False worldly assumptions can and must be confronted if we truly love. And, as an elder (at least in these cases) we speak as an elder would to a child. We don’t begrudge them their ignorance, nor do we want them to feel in any way ashamed of it. But, because we love them too much to leave them to a life of immaturity, we speak without compromising what is right in a gentle and loving way, lavished with encouraging vs condescending words. With practice, we’ll become successful even in first meetings with people as, all grown up, we expand the Kingdom of God.
_If I have the gift of prophecy and can fathom all mysteries and all knowledge, and if I have a faith that can move mountains, but do not have love, I am nothing. -1 Corinthians 13:2 (NIV)