1. Just because it's true doesn't mean it's your job to say it. Discernment from the Holy Spirit, and consideration for what your relationship is to the other person, is necessary. You are not the truth police. There are times a thing doesn't need to be said, but rather prayed over, because God is really good at bringing His kids to the place of understanding.
2. Just because it's true doesn't mean it needs to be said at all. Are you nagging? Is it your place? Is it helpful? Is it necessary? Is it really a big deal? Does it even matter?
3. When speaking the truth, it is helpful to focus on the main truth you want to share. Do not unload all the truth you know, or think you know, about a topic, or a person and his issues. Pick one or two. Too much is, well...too much.
4. Check your motive. Are you concerned for the other person or are you just frustrated? I think we can speak truths about things that frustrate us, but not while we are frustrated. T.I.M.I.N.G.
5. Speaking truth in a way that is destructive to another person, and blaming it on the Holy Spirit, isn't nice.
6. Be prepared to receive truth as well as dispense it. Otherwise, you lack integrity and may have no place sharing it in the first place. If you can't take it, don't dish it out.
7. Finally, be prepared to eat your words in the future, in the rare case that what you thought was true was, in fact, false. Because let's face it. Sometimes we get it wrong.
"When words are many, sin is not absent, but he who holds his tongue is wise." Proverbs 10:19.
I need that verse plastered all over my house.