The most important thing (the only important thing?) is the end result--and that someone reads it.
Of course, the process to get there is important, because, duh, it's how we get there! But any way you do it, if it turns out good, it's a good process.
It's your process!
Imitation is important - feel free to pick and choose from other people's processes - but in the end you're going to have to invent your own process that works for you. Don't be surprised if it evolves from one book to the next.
Your personality might help deciding which way to go.
As has been said before, there are two main ways to write a book. Outlining and Pantsing. And then there are a myriad of combinations and variants of those two...
What I've found (I've used both approaches) is that pantsing makes for a very messy first draft. You have to love picking your story apart, rewriting, moving stuff around, putting stuff together, experiment, throwing stuff away! And so on.
Pantsing can be a good thing though if your creativity takes time to get going and you feel that you don't have the ability to just be creative within the small confines of a single scene. If you have to have the whole organic flow from beginning to end, pantsing might be your way to write a book.
Outlining on the other hand (usually) limits the chaos of the first draft, although you're still going to have to write several drafts. However, outlining requires more of an on/off-switchable creativity that you can use to go in and just create that scene, then move on to the next scene that may be years later, some place else or with a totally different group of people. (Of course, with an outline you can plan your scenes in one order - jumping between plots, locations etc as you see fit - and then write them in an other order as to limit the amount of disconnect).
Personally I'm clinically impulsive, so pantsing turned into a pretty varied assortment of "stuff" (A.k.a. total mess!) Outlining fits me better since I can just go wild with that one scene and it's "contained" within a reasonable story structure.
The kind of book you're writing can suggest one way or another.
If your book has a complex plot with many twists (e.g. books in the crime/thriller genre), outlining the story first might be better to avoid having to throw so much away due to logic holes.
Other types of books might work better with pantsing.