A commonplace book is not a diary of reactions, nor a scrapbook of pretty lines. It is a place where you keep what you do not yet understand — the poems that will not leave you alone, the lines that seem to have been written for someone else's life and have turned up in yours. I have kept one for twenty years, and it is the only notebook I have never lost.

To start, you need only a bound book with unruled pages, a pen that does not skip, and the patience to copy poems by hand. Copying matters. Typing a poem is a way of filing it; handwriting it is a way of taking it inside. The slow work of the pen moves the poem from the page into the body, where it can do its real work. I copy the poem on the right-hand page, leaving the left blank for later notes.

The left-hand page is where the conversation happens. But the conversation is not a monologue of admiration. A commonplace book should contain argument, disagreement, and bewilderment. Write down what the poem refuses to tell you. Note the word that seems wrong, the line break that feels like a hinge, the turn you did not see coming. These are not defects; they are the poem's mechanism, and you have just put your finger on it.

Choose poems that resist you. A poem you love at first reading is a poem that already agrees with you; a poem that confuses you is a poem that has something to teach. Copy them all — the ones you adore and the ones you suspect you would never be able to write. Include translations and poems in languages you do not speak. The sound of an unfamiliar tongue on the page is a reminder that a poem is not only meaning; it is also a system of sound that the meaning rides on.

Annotation is the art of touching a poem without bruising it. The temptation is to underline everything, to write a paragraph on every stanza, to treat the margin as a forum for your opinions. Resist that. A poem is not a legal document; it requires no gloss. Annotate like someone who plans to reread this page in a year. Ask questions instead of making statements. What changes if this line is read as a question? Why does the poem shift tense here? And the best annotation of all — the one you will thank yourself for — is to write, "This is where I stopped understanding, and it is exactly the right place."

Use a pencil, and use it sparingly. A light vertical line in the margin to mark a passage you want to return to. A small squiggle next to a word that feels deliberate. A question mark in the corner for the stanza that resists you. Underline only the word or phrase that would, if removed, collapse the poem. If you find yourself underlining whole stanzas, you are not annotating; you are highlighting a book you are afraid to forget. Trust that the poem will stay with you in its entirety, and that your job is not to summarise it but to locate the tensions that make it live.

Rereading beats reading widely because a poem is not a piece of information; it is an experience that unfolds over time. The first reading gives you the plot, the second gives you the music, the third gives you the argument, and the tenth gives you the silence the poem is built around. A poem that rewards twenty readings will teach you more than twenty poems that reward one. Widening the net is useful when you are looking for what moves you; deepening the well is necessary when you are ready to be moved.

In practice, this means choosing a handful of poems each season and living with them. Keep them in your commonplace book. Read them aloud, in different rooms, at different times of day. Mark the lines that shift their weight as you change. You will find that a poem you remembered as celebratory is actually elegiac, that a poem you found obscure is merely precise. And when you reread what you wrote in the margins a year ago, you will see not only the poem but the person you were — which is, perhaps, the deepest reason to keep a commonplace book at all.

Take, for example, a poem like "This Is Just to Say" by William Carlos Williams. On a first reading, it is an apology for stealing plums. A commonplace book entry might note the apology's form: it is not an apology at all but a statement of fact. The second reading catches the phrase "forgive me" and wonders at its placement. The third reading notices the word "delicious" and feels the cold of the plum against the tongue. By the tenth reading, the poem is no longer about plums; it is about the impossibility of true apology, or the generosity of admitting desire. None of this appears in the text; it appears in the space between you and the text, which only rereading can open.

What you are doing when you keep a commonplace book is not curating a collection of literary artefacts. You are building a relationship with the poems that will hold your attention over years. Some of them will fall away; they were never yours. Others will deepen until they seem to have written themselves from your own experience. That is the alchemy of the commonplace book: it does not preserve the poem as it is, but as you have become through reading it. And that is why annotating lightly and rereading deeply are not separate disciplines but the same practice, turned toward different doors.