Before turning to those moral and mental aspects of the matter which present the greatest difficulties, let the inquirer begin by mastering more elementary problems. Let him on meeting a fellow-mortal, learn at a glance to distinguish the history of the man and the trade or profession to which he belongs. Puerile as such an exercise may seem, it sh

Don’t think about how to get things done, instead ask whether they’re worth doing in the first place He will hold a card back for years in order to play it at the moment when the stake is best worth winning. (Holmes; Charles Augustus Milverton) You must play your cards as best you can when such a stake is on the table. (Holmes; Charles Augustus Mil

The fatal mistake which the ordinary policeman make is this, that he gets his theory first, and then makes the facts fit it, instead of getting his facts first and making all his little observations and deductions until he is driven irresistibly by them into an elucidation in a direction he may never have originally contemplated.

“Checklist” routines for critical factors help - assuming I am competent enough to decide what factors are critical and that I can evaluate them

It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.

You’ll get results, Inspector, by always putting yourself in the other fellow’s place, and thinking what you would do yourself. It takes some imagination, but it pays. (Holmes; The Retired Colourman)

Don’t miss the forest for the trees - It is not the amount of information that counts but the relevant one.

I fear, sir...that, interesting and indeed essential as these details are, my inquiries must go more to the root of things. (Holmes;

More information isn’t necessarily better information but it may falsely increase our confidence - What is not worth knowing is not worth knowing A wise man sees as much as he ought, not as much as he can. (Montaigne)