Long before notebooks were for journaling, writers and thinkers kept commonplace books: collections of quotations, observations, facts, and ideas copied out by hand from their reading. John Locke wrote a treatise on how to index one; Milton kept one; generations of students, poets, and scientists filled them with the passages they did not want to lose. The practice faded with search engines, but it is returning, because copying slows you down, forces attention, and turns reading into thinking.

A commonplace book is not a diary. You are not recording your day; you are collecting other people's words and your own responses to them. A diary looks backward at your life, while a commonplace book looks outward at ideas, gathering raw material that your future writing can draw on. Over months and years, it becomes a personal anthology of what moved you.

Choose a format you will actually use: a paper notebook, a note-taking app, or a simple document. Paper has one advantage — handwriting slows you to the speed of thought and aids memory — but the best format is the one you reach for daily. Start small: one entry per day, or one entry per reading session. Copy the quotation accurately, note the source and page, and add a few lines of your own.

Organise lightly. A few broad tags or headings — on craft, on courage, on place, on work — are enough. Date your entries so you can trace how your interests change over time. Include more than quotations: striking facts, overheard sentences, images, questions, and your own half-formed ideas all belong, as long as each entry is something you want to return to.

A commonplace book pays off in unexpected ways. Stuck on an essay? Browse your entries for a quotation that opens it. Building a character? Your collected observations are richer than invented detail. Do not worry about making it beautiful or systematic: a messy commonplace book that you actually keep beats a perfect one abandoned after a week.

Reviewing your commonplace book regularly is what turns a collection into a tool. Once a month, read through recent entries and mark the ones that still resonate; you will be surprised how many have faded and how few still feel alive, and that filtering is valuable in itself. Copy the strongest entries into a second, smaller book or document, a best-of collection that grows slowly and represents your deepest interests. Some writers organise this distilled version by project, keeping separate sections for an essay in progress, a novel's themes, or a talk they are preparing, so the material is waiting when the work begins. The practice also pairs well with a reading journal, where you record your own thoughts rather than others' words; together they capture both halves of the reading experience, what the book said and what you thought about it. Over years, a commonplace book becomes a portrait of a mind: the questions you returned to, the writers who shaped you, and the ideas you refused to let go.