Carlos Castaneda's The Eagle's Gift seems to be the sixth book, although it followed several years past the initial five. This is structured differently from its predecessors (at least as I'm able to recall) in that Castaneda isn't working directly with Don Juan, but with his extended group, and the over-all course of the book is "tidying up things" as Don Juan and his associates prepare to "leave the world", a process which initially sounds like he's dying but actually is a major metaphysical undertaking involving a conceptualization of power called "The Eagle", which I don't pretend to really understand.
Towards the end of this book, Castaneda describes Don Juan speaking with each of his group individually, making sure that all are clear on the various aspects of their workings. On one level, this seems to be the point of The Eagle's Gift, as parts go through various aspects of dreaming, parts go though various aspects of stalking, and parts deal with the details of the structure of a "Warrior group", and how this relates to something called "the rule".
I know that it sounds like a huge cop-out, but much of the details have already slipped from my recall ... however, in the book it repeatedly notes that it is typical that the interactions with things in non-normal reality are quickly forgotten by the part of the mind which operates within normative reality ... frankly, much of the book deals with Castaneda trying to re-connect with stuff that he didn't know he did/learned/knew from various experiences, so I guess I'm in good company in my "forgetting"!
That said, the details are still in the book (yeah, and I suppose I could go through with note cards and research this, but I'm not going to at the moment), which makes it quite a good reference for the "Yaqui" (or what has more recently been re-packaged as "Toltec") methodologies framed as dreaming, stalking, etc. The fact that Don Juan, etc., (in a mundane temporal sense) exit the story line at this point, also make this something of the pivot-point between the "classic" first five, and the later works (often seen as being less "legitimate" or tradition-based than the original material).
It appears that this is still available in a paperback reprint edition, so you should be able to find a copy at your local bookstore, but I picked up the hardcover from the Amazon new/used vendors, and you can still get a "very good" condition copy there for around two bucks (plus shipping) if this sounds like it needs to be in your library too!