Another way of asking that: principles or applications?
The childish part within us would always like to know: what exactly do I need to do, say or write in order to succeed? How exactly do I ace the competition for this job? How exactly should I start my query to make it stand out from the hundreds that cross this agent's desk this day? How exactly do I start my book when more and more agents are asking for only the first five or ten pages? Etc.
The wiser part of us knows that what works for another may not work for us...or what works today may not work tomorrow...or what should have worked tomorrow will be called because of rain.
So it can be helpful to know assorted specific applications, though they may well already be completely out of date: pick-up lines, interview strategies, others' great queries or opening lines...These are useful to know, but we'd all be damned fools to set out on our own unique journeys with baggage trains filled with specifics that have worked for others.
I say let's set out with our back packs instead, lightly packed with principles that will endure and serve us well if we have the pluck and luck to forge our own specifics: E.g. : Grab the reader by the throat and never loosen your grip...In a query or an interview, think about You(the other) and not your own miserable Me-Me...Seduce, don't rape, the reader...Be brief, be blunt, be gone...Etc.
End note: I've never forgotten Robert S., a San Francisco businessman years before computers, or his massive, hand-carved desk. The desk's surface remained, almost always, completely empty--except for one thing: a 3x5 index card. On the card, carried in his shirt when not set upon the desk, were the figures he needed to tell him how exactly his business was going. Years later, I think of these figures as his principles. The enduring things that he needed to know. As for the applications--the daily decisions that he had to make--he remained perfectly fluid, guided by instinct and his own experience, not rules from books or others' words.
The lesson for today endeth with one more abiding principle: Always risk getting your face slapped for taking a chance on yourself.
The Electrifying New Internet Sensation