In 1685 English physician and philosopher John Locke published "Méthode nouvelle de dresser des recueils" in Le Clerc's Bibliothèque universelle II (1685). This was translated into English in Le Clerc's Observations (London, 1697). It was first published separately as A New Method of Making Common-Place-Books ; written by the late Learned Mr. John Lock, Author of the Essay concerning Humane Understanding. Translated from the French. To which is added Something from Monsieur Le Clerc, relating to the same Subject. A treatise necessary for all Gentlemen, especially Students of Divinity, Physick, and Law. There are also added two Letters, concerning a most useful method for instructing Persons that are Deaf and Dumb, or that Labour under an Impediments of Speech, to speak distinctly; written by the late Learned Dr. John Wallis. (London, 1706.)
Locke began keeping commonplace books during his first year at Oxford in 1652. On pp. [vi] and  of the 1706 edition we find a chart printed in red and black showing how he was able to create an expandable index of topics on two pages in each commonplace book. The index contained a line for every letter of the alphabet and for each letter there were sub-divisions based on the vowels a, e, i, o, and u. He described his method as follows:
"When I meet with any thing worth putting into my Common-Place-Book, I presently look for a proper Head. Suppose for Example, the Head were Epistle; I look in the Index the First Letter which the Vowel that follows, which in this Case E I. If there is found any Number in the Space marked E I, that shows me the space designed for Words which begin with E, and whose Vowel that immediately follows is I, I must refer to the Word Epistle in the Page what I have to take notice of, I write the Head in pretty large Letters, so that the principal Word is found in the Margin, and I continue the Line in writing on what I have to remark. I constantly observe this Method, that nought but the Head appear in the Margin, and on on without carrying the Line again into the Margin. When one has thus preserv'd the margin clear, the Heads, present themselves at First Sight" (1706 edition p. 6).
Locke's method of indexing his notes was reflective of styles of reading and note-taking characteristic of his time. According to a very widely quoted passage by Robert Darnton:
“Unlike modern readers, who follow the flow of a narrative from beginning to end (unless they are digital natives and click through texts on machines), early modern Englishmen read in fits and starts and jumped from book to book. They broke texts into fragments and assembled them into new patterns by transcribing them in different sections of their notebooks. Then they reread the copies and rearranged the patterns while adding more excerpts. Reading and writing were therefore inseparable activities. They belonged to a continuous effort to make sense of things, for the world was full of signs: you could read your way through it; and by keeping an account of your readings, you made a book of your own, one stamped with your own personality. . . By selecting and arranging snippets from a limitless stock of literature, early modern Englishmen gave free play to a semi-conscious process of ordering experience. The elective affinities that bound their selection into patterns reveal an epistemology — a process of knowing — at work below the surface" (Darnton, “Extraordinary Commonplaces,” New York Review of Books 47 (20)[December 21, 2000] 82, 86).
Locke's method of indexing commonplace books remained widely used for at least one hundred years. Toward the end of the 18th century English publisher John Bell published notebooks entitled Bell’s Common-Place Book, Formed generally upon the Principles Recommended and Practised by Mr Locke.” These included eight pages of instructions on Locke’s indexing method, a system which not only made it easier to find passages, but also served the higher purpose of “facilitat[ing] reflexive thought.”
♦ Reflecting upon Robert Darnton's comment, perhaps my personal reading and writing style is more representative of the seventeenth century than the twentieth or twenty-first. Throughout my career in the antiquarian book trade, which began in the 1960s, I found myself moving between subjects in the course of a day as I catalogued various books in stock, read about other books for sale, or discussed the different interests of clients. With access to the Internet in the 1990s it was, of course, possible to follow-up more efficiently on diverse topics with Internet searches and hyperlinks. The way that HistoryofInformation.com is written, as a series of reading and research notes connected by links and indexed in a database, may be viewed to a certain extent as analogous to the method of maintaining and indexing commonplace books described by Locke. ♦