Yes Sir / Yes Madam

Have you ever come across persons who are 'Baba Black Sheep Managers?' This phrase means a person who is always saying Yes Sir, Yes Sir / Yes Mam, Yes Mam, The eponymous character in the nursery rhyme was able to answer the question asked to him in the rhyme but in real life when persons keep on saying Yes Sir, Yes Sir for anything that is conveyed / told to them; it acts as an impediment to effective communication.
I wonder how do people fall into this trap of saying 'Yes Sir, Yes Mam'. Most of the time it comes out of nervousness when one is required to address a senior. They may sometimes even want to behave respectfully. This particular behavior of a person may backfire as it puts off the person who is being addressed. Rather than being taken as showing respect towards someone; the person may appear  submissive or may be even as a flatterer. Sometimes a senior may also assume it to be a part of your skill to show that you are lacking in the information / knowledge that is required of you as per your position.
Due to these reasons many multinational companies have made it a rule to call one another with their first names. In India we use 'Mr. -so and -so' as still many of the employees are not comfortable addressing others with their first name. The correct etiquette to be followed in such situations is to address the person as Sir / Mam if you feel awkward to call the person by the first name. Try to use the term sparingly by maintaining a polite and helpful tone.
The golden rule - use Sir / Mam not as an excuse for bad speech but as an adornment to a good speech. In case you intend to impress someone , make a meaningful and stirring conversation with that person rather than being the Baba Black Sheep who keeps on sirring around.