As factors in your career success, it's not just how competent you are, and it's not just about the words you say: no less important are the non-verbal messages you send . . . and read in others. I cover some of this in my books, but let me recommend "How 'Power Poses' Can Help Your Career"-- an excellent article with accompanying video from the Wall Street Journal.
The article is not--as you might suspect--about being a phony poseur, but rather about how to pay attention to the body-language and other non-verbal messages you are sending . . . and receiving.
One insight from the article: "Merely praticing a 'power pose' for a few minutes in private--such as standing tall and leaning slightsly forward with hands at one's side, or leaning forward over a desk with hands planted firmly on its surface-- led to higher levels of higher levels of testosterone and lower levels of the stress hormone cortisol in study participants. These physiological changes are linked to better performance and more confident assertive behavior, recent studies show."
And, the study found, these changes, practiced in private, tend to carry on after you leave the private area and go into a meeting (or sales call). This accords with what I've written about "mental rehearsals" in my book SMART QUESTIONS: People Skills for Winning the Games of Career Success (& Office Politics!)
For some ideas and visuals on sending and reading non-verbals and other types of body language, I suggest you check out Part Three: Communicating on Multiple Levels in my book SALES PRESENTATIONS & DEMONSTRATIONS. Awareness of body language is by no means only for sales people. Put another way, we are all sales people in a sense-- we are selling our ideas, our competency, our ability to work with others. And selling our determination not to be bullied by others in meetings!
Back to the Wall Street Journal and video that got this started: Link to the article and video "How 'Power Poses' Can Help Your Career" from the Wall StreetJournal