I use a perforated A7 memo pad (Maruman Mnemosyne N193A) to take transient notes while I’m out. Striking ideas from conversations, ideas while walking, and so on all get captured here. I usually include a bit of context to help orient me later: a date, a place, a person, etc.
These notes don’t stay in the memo pad: it’s effectively an inbox which feeds A writing inbox for transient and incomplete notes. Intermittently, during My morning writing practice, I process memo pad notes by developing them into Evergreen notes, by transferring them into my writing inbox, or by discarding them.
I tear off sheets as I process them, so I always know the notebook’s state: any non-blank pages still have to be processed.
Each idea gets its own tiny page. This helps me process them (Evergreen notes should be atomic): a good conversation might generate half a dozen memo pad pages, but each might require very different mental contexts to process.
I use this memo pad to help me Write about what you read. While reading a book, I’ll capture notes about what I find interesting in the memo pad. Each idea gets one memo pad page, as before. I also include a page number and date.
The memo pad fits easily in my pocket, and vinyl cover is quite durable, so I carry one at all times, along with a pen.
They have 50 sheets, so each sheet costs 4.5c. Not trivially cheap! A very interesting book might cost $2 to process. I guess that’s fine.
I use the Uni-ball Signo UM-151, which costs about a dollar. The pen feels well-balanced, its cap is reliable, it’s durable, and the inking action is very even.
So I always carry a small A7 tear-off notepad and a 0.5mm mechanical pencil (soft 2B leads) with me. This is my truly ubiquituous capturing device. I use it to take reading notes when I’m not at home, too.