It is essential that the tone of the conversation be set to one of agreement from the very beginning. If the first thing a person utters in response to your opening phrase is “No”, you can consider that trying to convince them of anything is totally out of the question. The person you are talking to has taken a different turning and there is no chance of them now going with the flow together with their conversation partner. It is important to start a conversation in such a way that the first word a person says is “yes”.