MIRROR. It creates rapport, but most importantly it unconsciously and inconspicuously triggers them to elaborate. It gives you the ability to disagree without being disagreeable. If you ask someone "What do you mean?" or "how so?" for example, you will be met with much more irritation or defensiveness. Start with "I'm sorry, (mirror), and then give some silence. I don't think you always need "I'm sorry" but the point is to say it as if you are misunderstanding their statement. An inquisitive, "please help me understand," tone.