Be a skillful salesman of true ideas about yourself always, even in the most casual relations you have with other people. Sell the best possible impressions of yourself to passers-by on the street, to your fellow riders in cars, to clerks and customers of stores you visit, to your home and business associates. Put selling skill, as second nature, into each word, tone, and action of your social and business life.
Realize that in whatever you do or say, consciously or unconsciously, you _are_ selling ideas about your capability or your incapacity. You are making more or less definite impressions--you are affecting your opportunities to succeed, and are forming good or bad habits--all the time. _Control the effects of your words, tones, and acts by saying and doing, consciously and intelligently, only what will aid in selling true ideas of your best capabilities._.
Of course you already know that each word and tone and act of your life makes _some_ impression on the people who hear or see you. But probably you have not realized fully that _particular ways_ of saying and doing things have _distinct and different effects_, each governed by an exact law of psychology. You perhaps do not know now _just what_ impression is made by a certain word, or tone, or act. To be a master salesman of yourself you need to study the science of mind sufficiently to acquire _working knowledge_ of common mental actions and reactions. Familiarity with at least the general principles of psychology is of the utmost importance in using the selling process effectively.
Do not shy from study of the science of mind because it is an "ology" and therefore may seem hard. _You are a psychologist already_. You know that certain things you do and say make agreeable or unfavorable impressions on other people. In a _general_ way you know _why_. It is necessary only that you analyze _specifically_ what you realize now rather indefinitely. If you do not care to study a _book_ on psychology, just use your own mind as your psychological laboratory for continual self-analysis.
Answer for yourself such questions as, "Exactly what effect will this particular word, or tone, or act have--and just why?" You can work out pretty well the _practical knowledge of psychology_ you must have in order to sell ideas about your capabilities most effectively. You simply need to apply _purposeful intelligence_ in everything you do and say; instead of making impressions without comprehending that by each word and tone and act of daily living you are influencing, favorably or adversely, your chances to succeed.