Yeah, wolfenshire hit the nail on the head; basically do what works for you, but also stay active.  The only problem I see with the How To books is not the books themselves, but a potential reader's approach to them.  You're already the expert on your own writing, and so no book is going to tell you anything useful.  You probably have more of an idea of what you want to accomplish or what you want to avoid, and so books on how to do it, will be redundant or unnecessarily intimidating.  And besides, most of the "great" writers probably had no clue what they were doing.  You can always look at those flow chart/story outline things, that DIY books love to throw at you but are all stories really like that?  And if you're writing post-modern fiction, then you can throw those "story structure" diagrams out of the window, or turn them over and scribble notes on them, since a lot of post-modern stories are non-linear with no rising action (and in some cases, no action at all...back in the 70s, in New Wave science fiction, there were whole 20-page stories written in which the characters never moved a muscle, not even to breathe) and in terms of flash-fiction or micro-fiction (really, really short stuff under 250 words) any story-movement is likely to be emotional or psychological rather than physical...and so...there's another story diagram out the window.  So in short, trust your gut.

As for what books tell you: if they make writing easier, they're working, and by "easier" I mean, less of an odious chore.  Writing is never "easy" but it shouldn't be impossible either.