Hmm, never tried to write a self-help book before, but one thing I’m wondering is, are you envisioning this as a sort of guide where someone reads through the book, front to back, as they do NaNo? Or is it more of a reference book, where they could read each section in any order?
If you’re doing the former (a guide that’s read front-to-back), then I would say you need to do more planning of the order, thinking about what’s the essentials that someone needs to know right away, what builds from there, etc. For example, you’d definitely want to talk about prepping up front, but wouldn’t need to talk about writer’s block until later on. (No Plot? No Problem! is largely organized this way, the first section is general but the second half is organized by week of NaNo)
If you’re doing the latter, more of a reference guide style, then the order doesn’t matter so much, and I’d focus more on writing up each topic separately, and figuring out the best way to group/order them later on.
Regardless of whether you’re writing a general book about NaNo or are focusing on a specific aspect (e.g. plotting methods or managing life/stress during NaNo), I would take some time to think about what your central goal is with this book. Write it down and think about it, and use it as a guide to know what to include or exclude. Think about what the reader will need to achieve that goal–those will be your topics. Then think about what the reader needs to understand those topics… and so on.
For example, let’s say your goal is “the reader should be able to complete NaNo with minimal stress”. What does a person need to achieve that goal? Immediately I’m thinking about things like time management, methods for increasing your words per hour, focusing on “good enough” words instead of “perfect” ones, and life tips about balancing necessary activities (cleaning/cooking/laundry!) with NaNo without letting your house become a disaster zone. But I wouldn’t include topics like pushing for a super high wordcount or becoming an ML, because those don’t fit the theme/central goal of “no-stress NaNo”.
(As I write this out, I realize this is basically the same advice as for plotting a novel… just the “theme” is what you want the reader to learn, and the “character arc” is hopefully that of the reader, not a fictional character!)