It is important to keep accurate records of your cases

Watson refers repeatedly to my records. He refers to the index in which I kept records of people and places [SILV], to my records of crime [FIVE], to my commonplace books containing cuttings [ENGR, MUSG], old notes [STOC], scrap-books and reference books, including an index of biographies [EMPT], row of year-books and dispatch-cases full of documents [VEIL], his own dispatch-case full of documents [THOR], and index volumes containing records of old cases, mixed with the accumulated information of a lifetime [SUSS].

From time to time, he mentions my activities with respect to those records - cross-indexing my records of crime, pasting cuttings in my common place books, and classifying past results, and makes snide remarks about how untidy they are. However, at no point, does he describe my system of documentation as a whole. It is based on the general principle which follows:

Keeping content in records keeps your mind clear for putting content into context.

--- a man should keep his little brain attic stocked with all the furniture that he is likely to use, and the rest he can put away in the lumber room of his library, where he can get it if he wants it [FIVE].
I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose - A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has difficulty in laying his hands upon it. Now the skilful workman is very careful indeed as to what he takes into his brain-attic, He will have nothing but the tools which may help him in doing his work --- there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones [STUD].
The barrister who has his case at his fingers' ends and is able to argue with an expert upon his own subject finds that a week or two of the courts will drive it all out of his head once more [HOUN].
The satellite brain of your library is useless, however, if you can not get the information you want when you want it. Hence the need for organizing and cross-indexing it.1 The making of records should be done on the spot, as soon as the information is available, so that it will not be erased or distorted by the passage of time. Watson describes how I jot down figures and memoranda [SIGN] and write notes on my shirt cuff [NAVA].

Inspector Mason expressed amazement that I would know the name of the manufacturer of a gun used in a common case: Do you carry the names of all the gun makers in the world in your memory? [VALL]. Not intentionally - this is the type of trivia to be sub-contracted out to the satellite brain. However, some of it sticks - to my embarrassment - one can hardly prevent some such stuff sticking as one browses through the files. Sometimes our 'forgetory' does not work. My favourable comment on Bennett's note-keeping was sincere [CREE]. However, when I expressed admiration of the stockbroker clerk for memorizing the stocks, I was of course flattering him for my own purposes [STOC]. Such information which varies from day to day is a sure candidate for the satellite brain. When Watson failed to recognize the name 'Killer' Evans, I said It is not part of your profession to carry about a portable Newgate Calendar in your memory [3GAR]. Nor, I must add, is it part of my profession. However, such information should be in my satellite memory to find when I need it.

1   My own system is called the Siliclone - that is, a silicon clone of myself. It consists of ten HyperCard stacks - labelled Notes, Quotes, Anecdotes, Images, Sources, Resources, Speak, Listen, Write, Read. It is represented by ten drawers in a filing cabinet (with ten drawers corresponding to those stacks) with an in-out box on top. Clicking on the out-box enables me to pull out relevant Notes, Quotes, Anecdotes, etc. on the various subjects in which I am interested. Such a system was not available to Sherlock Holmes but I am sure he would have loved it!