Avatar Na'vi language

It seems that a big chunk of Avatar movie budget went for creating the Na'vi language (by experts, apparently).
Anecdotical, it seems that the Na'vi language inventors were coaching the actors to speak it.
The fact, remarkable in itself, raises generic questions about this labguage in special, and new languages in general (or old languages, Hebrew being a perfect example).
I always wondered what would be involved to create a new language?
What wold be the production rules, the grammar, morphemes, etc?
It should be in a class already established (satem, centum)?
In any event, some lucky dudes got their chance.

Ever hearda Esperanto? You're laxed way if you havnt... Nothing new in that Navi dongerwonger either. Rather stupid too. Oudda'v just had the actors spit gibberish and shimbo, why bother making that crapajack language, whoda they think they are well... or they couda'v had em speak Esperanto.... thadd elicit a lot more booming guffaws from the spectators I'd say, cause that boldocks Navi fudgemunching is over the top and uncalledfor.