Michael Bierut, a longtime Pentagram partner and one of the best-known graphic designers alive, keeps his notes in ordinary office-supply composition books. In 2008 he wrote that he was on number 85 since 1982, that he can't walk into a meeting without the current one in his hand, and that he hates gridded paper, though not as much as lined. There is no correct notebook for design work. There are five decisions, and it helps to know what each one changes.
Blank, lined or dotted
Lines help you write straight and get in the way of everything else: a wireframe, a logo or a character doesn't fit between rules. That's why sketchbooks are almost always blank. A grid helps with floor plans and interfaces, and dot grid has been tied to bullet journaling since 2013, when Ryder Carroll, a digital product designer, published his method. If you draw more than you write, go blank. If you do both on the same page, also blank: you can write on a blank page, but you can't stop seeing the lines on a ruled one.
How heavy the paper is
Paper weight is how much one square meter of it weighs. Office paper is around 80 g/m², and many well-known notebooks use between 70 and 90. With that paper two things happen once ink is involved: ghosting, where you can see your writing from the other side even though the ink hasn't gone through, or bleed-through, where it has. Drawing guides put paper that can take finished work in several media at around 100 to 130 g/m², and ask for 130 or more for markers and ink. Weight isn't everything, because the paper's finish matters just as much. The real test is a page at the back of the notebook with the pens you actually use.
How it's bound
A glued notebook is a block of sheets with adhesive on the spine and, with use, it sheds pages. A sewn one is made of folded sections stitched together with thread, so it survives years of opening and closing without losing sheets. How far each one opens depends on the spine and the cover, so if you draw across both pages it's worth trying one before you buy. Spiral binding is the one that opens all the way, at the cost of rings that sit in the middle of the drawing and snag in your bag.
What size
A5 (14.8 × 21 cm) fits in any bag and runs out of room for sketching. A4, close to US Letter, is comfortable on a desk and awkward away from it. In between sits B5 (17.6 × 25 cm), and Bocetta's 17.6 × 24.5 cm format is practically B5: it has almost 40% more surface than A5 and still fits in a backpack. People who teach drawing put it simply: the largest one you can comfortably carry.
What color the page is
It's the decision almost nobody makes, because almost every notebook comes in white. But drawing on a colored ground is an old practice: draughtsmen in 16th-century Venice used blue paper because it gave them a middle tone to start from, and they added the lights in white. Drawing teachers say something similar about toned paper today: it takes away the fear of the blank page, because it doesn't feel blank.
That's where ours comes in. Bocetta is a notebook that's one color all the way through, with black or cobalt blue pages, and you work on it in light ink. It measures 17.6 × 24.5 cm, has 160 blank pages of 120 g/m² paper and is sewn.
It isn't for everything. If you take long notes in small handwriting, a white page reads better. If your work is linework, lettering, idea maps or sketches you want to see with fresh eyes, a dark ground is worth trying. See the notebook, or read what's known about the color of the page before you pick one. If you're torn between colors, the quiz takes a minute.
The one you'll actually use
People who draw every day repeat a piece of advice that cuts against nice notebooks: don't be precious with it. Bierut fills plain composition books with phone calls, meetings and estimates, all jumbled together, and illustrators who teach ask for the same thing, a notebook you're not afraid to make mistakes in. The best one is the one you open without ceremony. If a color makes you open it more often, that's a good reason to choose it.
Sources: Michael Bierut in Design Observer, Proko's guide to sketchbooks, Creative Bloq, Walsworth on sewn binding and the University of St Andrews exhibition Venice in Blue.