I finally finished reading all of NeotrekkerZ's Na'vi in a Nutshell. It's been out for a few weeks, but I hadn't finished reading it to give my full take, and now I have finished! This is the best guide I have read on learning Na'vi since I started scouring the internet for information after seeing the movie opening night.
Na'vi, like almost any conlang, is simply not developed enough to teach in the traditional classroom sense. In a classroom you learn grammar, exceptions to grammar and idiomatic phrases in a much more roundabout way. Since we can't do that with Na'vi we must take a much more direct approach. Na'vi in a Nutshell is broken down into sections on parts of speech (nouns, verbs, adjectives, etc), and it goes through all of Na'vi's cute little adpositions and infixes in a more or less logical order. There's even a skills test at the end to see how much you've learned. I haven't taken it yet. I want some more time for it to sink in before I'm struck with the realization that I still don't get it :)
The one draw back of course is certain sections are pretty heavy on the linguistic terminology. I'm no professional linguist, so sometimes that terminology goes over my head. There were a few places where I had to read it a few times, but for the most part I was able to get it from a practical perspective. And there's always Wikipedia to remind myself what certain terms mean.
So if you are interested in Na'vi, go check it out! After reading it I feel much more confident in how all the pieces fit together.
The way this guide is layed out is actually my preferred method to introducing myself to a new language. Not having a backbone like this is what caused me to give up on Japanese. I could never understand it because they only teach you the polite forms first, so I couldn't reason out the basic structures that I feel like I should have known after a 101. I definitely want to pick it up again someday, but right now I'll just stick to the random things I've gleaned from watching subtitled anime.