i think a lot of us have an enormous collection of things we meant to think about later. a paragraph photographed in a library book. a sentence in our notes app. an interview saved somewhere between a recipe and an apartment we cannot afford. we clearly found these things interesting. the problem is that we rarely see them again.

a commonplace book gives you somewhere to put the parts you want to keep, along with your own thoughts about them. you can collect passages, questions, observations, definitions, little arguments. and you don’t need to be particularly well-read to begin. having somewhere to work through what you’re reading might actually help with that.

this is how i would start one without making the whole thing so elaborate that you need a quiet weekend and a new personality.

choose somewhere you can write comfortably

a plain notebook is enough. so is a document on your laptop. choose according to how you already behave, because that is probably more useful information than which setup looks nicest in a photograph.

if you underline physical books and like writing by hand, use a notebook. if most of your reading happens online and you want to search your entries, a digital document may be easier. you can also use both, although i would give each one a clear job. perhaps the notebook holds your finished entries and your phone collects things temporarily.

check the practical details before buying anything. does the notebook open comfortably? can you read your handwriting on that paper? is it small enough to take where you read? a beautiful notebook that makes writing awkward will become a beautiful object you avoid.

begin with something you already care about

you don’t need an impressive opening quotation. find something you have recently wanted to talk about.

perhaps a character made a decision you couldn’t understand. perhaps an essay described a feeling you thought was peculiar to you. perhaps you read an opinion that irritated you and then realized you couldn’t explain why.

that is an entry.

write down the passage, or summarize the idea accurately if it is too long. then explain what caught your attention. “i keep thinking about this because…” is a perfectly useful first sentence. you can work with an unfinished thought. you do, however, have to let yourself write it down before you know exactly where it leads.

give each entry four little parts

i would keep the structure very simple:

• the passage or idea
• where you found it
• your response
• something to follow up

for a book, record the author, title, and page number if your edition has one. for an online piece, save the author, title, and link. include the date when it matters, particularly if you are collecting something about current events.

then add your response. what do you think the writer means? what makes the idea convincing? does it remind you of something else? what would you ask if the author were sitting across from you?

the follow-up can be tiny. look up a word. reread an earlier scene. find the painting mentioned in the paragraph. give your curiosity somewhere specific to go.

write more than “i love this”

you are allowed to love a sentence because it is beautiful. i certainly do. but try explaining what you love about it.

does the writer name something you have experienced? does the sentence move in an unusual way? is there one ordinary word doing an unreasonable amount of work?

even two sentences of explanation make the entry more useful to your future self. you might return months later and discover that your interpretation has changed, or that the passage mattered because of something happening in your life at the time.

“i love this” tells you that you had a feeling. a little explanation helps you remember what the feeling was attached to.

let subjects emerge before making sections

i would resist dividing a new notebook into twelve permanent categories. you may think you need fifty pages for philosophy and then spend the next three months fascinated by houses.

number your pages instead. leave a few pages at the beginning for an index, and add subjects as they appear. an entry about a novel might belong under friendship, ambition, and money. you can list the page number under all three.

digitally, you can do something similar with a short list of tags or a simple contents page. keep the vocabulary consistent enough to find things again. you probably don’t need separate categories called “identity,” “selfhood,” and “who am i becoming” during your first week.

include observations from your own life

books are not your only source of material. a conversation can give you something worth examining. so can a visit to a museum, an advertisement, or a detail you keep noticing in films.

be specific about what happened before you interpret it. “everyone is obsessed with status” is a very broad claim. describing how people introduced themselves at one event gives you an actual observation to consider.

also, separate what you witnessed from what you assumed. someone being quiet does not tell you why they were quiet. i think this is a useful habit generally, especially when our minds are feeling unusually qualified to narrate other people’s motives.

revisit a few entries each week

you don’t have to write every day. i would rather have three entries i can use than a daily obligation i begin resenting by thursday.

once a week, read back through a few pages. add a thought in the margin. connect two entries. notice whether a question keeps returning in different forms.

maybe you have collected five passages about women and money without consciously deciding to study the subject. now you have a reason to choose your next book. maybe something you believed last month already feels incomplete. write that down too, with the date.

the revisiting is where your collection starts helping you think.

make your first entry today

choose one passage you already have saved. record its source. write three sentences about why you kept it, and finish with one question.

that is enough for a beginning. you can make an index later. you can change notebooks later. you can discover that the system you imagined is too complicated and simplify it.

i like the thought of having a place where my interests have some continuity. where a sentence i read in march can meet something i notice in october. where i can find evidence of what i used to think, rather than relying on my suspiciously flattering memory of it.

start with the thing you keep returning to. give it a page.