Deference
To be respected as a professional, we should show respect to the people around us, as people will tend to treat us the way we treat others. The behavior of showing respect to others involves demonstrating deference to the people we encounter, which might be based on their title, tenure, experience, education, or expertise, or the simple fact that they are another human being deserving of our respect.
There are many ways to demonstrate respect, depending on the situation and the person you are speaking with.
For example, if you happen to know that someone has earned their medical degree, addressing them by their title and last name would show deference to their accomplishment of completing a grueling educational program. In practice, this means that instead of addressing someone by their first name of "Sam," you would call them, "Dr. Smith." If Dr. Smith would prefer for you to call them Sam, then they can tell you that, but you should default to showing them the respect they have earned.
Similarly, if you are interacting with a member of law enforcement, you would show respect to their position by addressing them as "Officer," or by reading their badge and addressing them as, "Officer Johnson." If an officer had a higher rank of "Captain," then it would be appropriate to address them as "Captain," or "Captain Jones."
By using the title that shows respect for someone's accomplishments or position, we set the precedent that we expect others to respect our accomplishments and position. For example, if you earned a PhD in economics, and were attending an economics conference with many other PhDs in attendance, if you chose to not address anyone as "Doctor," you should not expect anyone to call you, "Doctor."
Where showing deference can become a bit tricky is when dealing with people across different generations, as older generations tend to want more traditional demonstrations of deference, such as a younger person addressing them as Mr., Mrs., or Ms., or even Sir or Ma'am. Over time, these traditions may fade away - much as did addressing someone as "Master" or "Mistress" - but suffice to say, be sure to not accidentally offend someone older than you by not being sensitive to their expectations. Just as with title, it would be better to address an older person as, "Mr. Williams," and then have them tell you, "Mr. Williams is my father - just call me Carl," than to address Mr. Williams by his first name, and have him consider you a rude young person.
In addition to showing respect for someone's title, you should also defer to people who know more than you do - or at least should know more than you based on their background. This can be a difficult thing to remember, especially when you are highly competent and confident in your skills - but people often find it very endearing to have someone show them respect when they don't have to.
Imagine two aeronautics engineers, one who just graduated from an elite technical university, and the other close to retirement. Both have a claim to not show deference to the other: the younger university graduate might think the older engineer's skills are obsolete, their opinions out-of-date, and that they should just sit in the corner and wait for retirement. The older engineer might consider the younger engineer to be too inexperienced and untested to have anything of value to contribute, and might therefore treat them like someone good for not much else than fetching coffee.
If the older and younger engineers choose to not show deference to each other's accomplishments - be it showing respect for the younger engineer's more recent education, or the older engineer's many decades of experience - they would most likely not work well together, or work together for very long.
If instead, both of them approached each other with deference, the younger engineer may say, "I'm thinking of using a composite ceramic for this part, and titanium for this part, what do you think?" By simply asking the older engineer's opinion, deference is shown.
The older engineer in turn might show deference by saying, "Titanium is a good choice, but to be honest I haven't had much experience using composite ceramics. Tell you what, I can help you design the titanium part, and you can teach me about composite ceramics - how's that sound?"
As they both banter back and forth, both engineers will soon forget about the differences in their education and experience, and instead of thinking about who is young, and who is old; or who has more recent education, or who has more years of experience, they will simply come to regard each other as professional colleagues.
By showing deference to others, people will consider you pleasant, polite, and respectful - all of which contribute positively to your professional reputation. People like to work with people who show them respect, and when they are shown respect, people will tend to return that show of respect in kind.
Even beyond respecting someone's title, tenure, experience, education, or expertise; there is a base level of respect that we should show to everyone we meet, even if they don't have an impressive title, what they do for a living isn't glamorous, and their education isn't extraordinary.
If we happen to pass a janitor in the hallway, we should show them the same deference as we would the CEO of the company, as everyone is deserving of respect, and everyone appreciates being shown respect. If every morning, you wave to them, ask them how their day is going, and wish them well, word will get out that you are a kind person, that you respect the people around you, and if for no other reason, you too are deserving of respect.
People always appreciate when you acknowledge them, and people will always think highly of someone who is respectful towards others. These are basic human social skills that every professional should seek to master, as they not only help build a positive professional reputation, but also contribute to the world being a better place.