Some patterns don't change over time or wisdom from the past

One of the most prominent thinkers of the 18^th century, Philip Dormer Stanhope, 4th Earl of Chesterfield (mostly known for his "Letters to his son") made multiple intriguing observations concerning people’s conduct in the society. I’d say many of his thoughts answer the question about how to be valuable for the people you are interested in (i.e. your target audience). 

I’d like to place here some of the most valuable quotes from “Letters to his son”.

  

• “He makes people pleased with him by making them first pleased with themselves.” 

• “Never seem more learned than the people you are with. Wear your learning like a pocket watch and keep it hidden. Do not pull it out to count the hours, but give the time when you are asked.” 

• “Take the tone of the company you are in.” 

• “Every woman is infallibly to be gained by every sort of flattery, and every man by one sort or other.” 

• “Women who are either indisputably beautiful, or indisputably ugly, are best flattered upon the score of their understandings; but those who are in a state of mediocrity are best flattered upon their beauty, or at least their graces; for every woman who is not absolutely ugly thinks herself handsome.” 

• “You will find that reason, which always ought to direct mankind, seldom does; but that passions and weaknesses commonly usurp its seat, and rule in its stead.” 

• “Knowledge may give weight, but accomplishments give luster, and many more people see than weigh.” 

• “In the ordinary course of things, how many succeed in society merely by virtue of their manners, while others, however meritorious, fail through lack of them? After all, it's only barbarians who wear uncut precious stones.” 

• "There is nothing that people bear more impatiently, or forgive less, than contempt; and an injury is much sooner forgotten than an insult." 

• “Style is the dress of thoughts.” 

• “The vulgar look upon a man, who is reckoned a fine speaker, as a phenomenon, a supernatural being, and endowed with some peculiar gift of Heaven; they stare at him, if he walks in the park, and cry, that is he. You will, I am sure, view him in a juster light, and nulla formidine. You will consider him only as a man of good sense, who adorns common thoughts with the graces of elocution, and the elegancy of style. The miracle will then cease.” 

• “The receipt to make a speaker, and an applauded one too, is short and easy.—Take of common sense quantum sufficit, add a little application to the rules and orders of the House, throw obvious thoughts in a new light, and make up the whole with a large quantity of purity, correctness, and elegancy of style.” 

• “The company of women of fashion will improve your manners, though not your understanding; and that complaisance and politeness, which are so useful in men's company, can only be acquired in women's.” 

• “Half the business is done, when one has gained the heart and the affections of those with whom one is to transact it.” 

• “Deserve a great deal, and you shall have a great deal; deserve little, and you shall have but a little; and be good for nothing at all, and I assure you, you shall have nothing at all.” 

• “Pleasure is necessarily reciprocal; no one feels it who does not at the same time give it. To be pleased, one must please. What pleases you in others, will in general please them in you.” 

• “By all those, who are not much acquainted with him, he was considered infinitely below his level; he put no price upon himself, and consequently went at an undervalue; for the world is complaisant or dupe enough, to give every man the price he sets upon himself, provided it be not insolently and overbearingly demanded. It turns upon the manner of asking.” 

• “Most people enjoy the inferiority of their best friends.” 

• “I recommend to you, in my last, an innocent piece of art: that of flattering people behind their backs, in presence of those who, to make their own court, much more than for your sake, will not fail to repeat, and even amplify, the praise to the party concerned. This is of all flattery the most pleasing, and consequently the most effectual.” 

• “Never seem wiser, nor more learned, than the people you are with. Wear your learning, like your watch, in a private pocket: and do not merely pull it out and strike it; merely to show that you have one.” 

• “The talent of insinuation is more useful than that of persuasion, as everybody is open to insinuation, but scarce any to persuasion.” 

• “The best way to compel weak-minded people to adopt our opinion, is to frighten them from all others, by magnifying their danger.” 

• “If you would be a favourite of your king, address yourself to his weaknesses. An application to his reason will seldom prove very successful.” 

• “If you can once engage people's pride, love, pity, ambition (or whatever is their prevailing passion) on your side, you need not fear what their reason can do against you.” 

• “It is to be presumed, that a man of common sense, who does not desire to please, desires nothing at all; since he must know that he cannot obtain anything without it.” 

• “Endeavor, as much as you can, to keep company with people above you.... Do not mistake, when I say company above you, and think that I mean with regard to their birth; that is the least consideration; but I mean with regard to their merit, and the light in which the world considers them.”