One of the first essays about creative writing I ever read was "On Keeping a Notebook" by Joan Didion. It's one of the most influential pieces I've read.
In the essay, Didion discusses how keeping a little notebook with her at all times has affected her writing life and overall creativity.
Your notebook, as a writer, is a private place where you can record novel ideas, snippets of conversation to recreate in dialogue, and wayward thoughts with no discernible shape that could come in handy some day.
In Didion's words: "We are talking about something private, about bits of the mind's string too short to use, an indiscriminate and erratic assemblage with meaning only for its maker" (3-4). The notebook is for your own personal benefit. You don't have to show it to anyone else.
What do you think of keeping a writer's notebook? Do you have one? What do you put in it? How do you think it has helped you as a writer?