A major part of the success you get in communicating with others depends on the style and language that you use in your communication. If you are talking to your supervisor explaining him a situation, you will agree that you won't use the sentences you use when you are talking to the neighborhood greengrocer.
What you say, combined with the way you say it, determines how the listeners perceive your message. There are times when the speaker has to be firm, and there are times when he has to be friendly. There could also be times when you have to exercise authority, but it is advised to keep listening intently and empathize whenever needed in all these cases.
Always remember that a person reacts under certain circumstances. In other words, circumstances dictate a person's behavior. Trying to communicate with “hmmm” without trying to understand the condition he is in will only lead to a massive fall-out.
Successful people have mastered the art of a “You win, I win” conversation, where they will listen, establish a common ground by empathizing and then finding a way to put their proposal through, without hurting anybody’s sentiments. That is only possible due to their constant understanding of the issues the listener is facing and partly consoling, partly validating, and part realizing the issues themselves.