These tips aren't mine, they were created by tsmukan Atantsawkeyä. Some of them which I have seen before really helped me to learn the language, so I want to show those here. You can see the original text in russian
here. Also I want to thank tsmukan KalaKuival for correcting my translation
Appeal to everyone who begins to study Na'vi
You are beginning to learn the Na'vi language. At your disposal is the vocabulary, grammar, and quite a large number of phrases. But before you start to learn the new language, please read these tips. They will help you master the Na'vi language faster and easier.
Na'vi is a constructed language, but it doesn't mean that it's primitive or frivolous. It has a vocabulary, the grammar, rules of pronunciation, the way of writing the words and its own peculiarities of expressing thoughts. The Na'vi language is not tied to the "Avatar" movie. You can talk on any topic in your everyday life in this language. This is a serious, independent and developing foreign language and to master it, you will need to put serious effort in this.
You will need to remember a lot, and it's not always easy. You'll certainly succeed, if you summon patience, perseverance and discipline on your side.
1.
Vocabulary. Do not even try to learn words in the alphabetical order, it's time consiming and the most difficult way. The words in the dictionary are arranged in alphabetical order only for the purpose of making it easier to look for translation. Rather open the dictionary and scan it from beginning to end.
Do not learn the words that seem to be rare or too specific for you. When you encounter those somewhere, just look them up from the dictionary on the way.
Write down the most commonly used words and their translations. You'll get a list of about a hundred or a little more words. You will already be able to express simple thoughts with them. Read the list again from the beginning to the end and try to group words as you think suits best. For example, write the words separately for the colors, the most common verbs (to be, to go, to eat, to see, to hear) etc. Beside each word write a sattelite word, if possible. Satellite word is a similar or related word by value or use. For example, "to run" and "running".
Never memorize words one by one! This is the most certain way to forget them, or even worse - confuse them.2.
Time. If you take up studying Na'vi, there is only one way to do it: learning to speak, read and write perfectly. Nothing can be acheived without effort. Studying of Na'vi takes time, so spend some 20-30 minutes a couple of times a day and later on make a longer session of 1,5-2 hours. Doing less is impossible, as otherwise you will forget things you will have learned. 2-3 times during the day try going through what you have recently studied. Repeat the words, sentences, remember the material you had studied from the previous day and the day before that.
3.
How to memorize. The only effective way to memorize the words in Na'vi is to use them. An analogy can be found in the cooking: cook may get and lay out products, but the dish will only be ready when all the ingredients will be mixed together. If you memorize a word alone, you are wasting your time. You will not be able to quickly employ it in speech. All the words you study, absolutely every single one, you should use in a sentence. Do not be afraid for not knowing the grammar in detail. Create at least one simple phrase with a new word, and remember this phrase as a whole.
When you did not use a new word in a sentence - then don't remember it at all. Make a rule to create a phrase or a sentence with every new word. This rule should not be broken. Ever.4.
Grammar. Although the Na'vi guide exists, it helps you only with the basics. The fact is that the grammarbooks of any language are written without considering how necessary it is for you. It may seem to be easier to study on already written grammar rules, but that is only an apparent ease. Books facilitate learning for groups of students, but you learn Na'vi independently, and the book would just slow you down.
Material from the book is difficult to remember, because you have to memorize things the way it seemed to be best for the authors, not by the way you are used to. Now what you would have to do is to read the rules of grammar, and then gather them together and organize as seems best for you. It is difficult, but believe me, it really works.
Note: Studying grammar separately is pointless. It's sensible only in one case: if you really like it and you want to study it. First read the rules, and then try to write your own examples, draw your own schemes of rules.5.
To speak. Your ultimate goal is to speak Na'vi with other people. So you will have spoken out loud anyway. Pay special attention to pronunciation and the rules of reading words in Na'vi. Listen how other people are speaking and repeat it aloud. If someone curious asks what you are mumbling about, respond proudly that you are learning a foreign language. It may sound strange and unusual at first, but this is normal and fades very quickly.
When talking to someone don't be afraid to make mistakes. Sooner or later you will make them anyway. No one will laugh at you, because almost everyone has gone through this phase. This just cannot be avoided. Remind yourself that you are learning the language not in order to nurture your ego, but to know it perfectly.
Speaking Na'vi aloud helps you better memorize the words and gradually become as good as Neytiri or Tsu'tey. And mistakes help you better understand what needs to be improved. 6.
Too much unknown. From the first day of your studies in Na'vi you will find unfamiliar notations and concepts of linguistics. In this case you may feel confused. Here's what to do in this case: look up every unfamiliar concept from Google and understand it's meaning. Don't worry, grammatical terms are less important than the knowledge of words and the ability to build phrases. Do not be confused by unfamiliar concepts.
7.
Basics of language. In Na'vi some words form are the basis of almost every sentence. These are verbs like "to be", "to think", "to go", "to want", "to speak", "to see" and others, which are used very often. Also the personal pronouns ("I", "we", etc.), indeterminate-personal ("someone", "somewhere"), interrogatives ("who?", "why?", "where?"). This is the so-called lexical basis of language or vocabulary at least.
Rule in respect of these basic words is this: you need to memorize them all sundry. This means that you need to make at least 5 sentences with each pronoun, each verb, etc. And remember these phrases by heart. Otherwise further studies in Na'vi will be slow and difficult for you. Next, see paragraph 8.
8.
Remember forms of verbs. Na'vi has an unusual way of creating different verb forms. Simply speaking, the verb is "torn apart" and inserted a syllable. For example, lu (to be) becomes lamu (l<am>u) in the past tense. At the end of the dictionary you will get acquainted with all the means for the formation of tenses and other forms of verbs. You probably will want to remember how to create the past tense or, for example, the future tense separatedly.
DO NOT DO THIS! You'll never be able to speak normally if you create the verb forms on the run.
It's better to make notes for at least basic aspect, tense and mood forms for most common verbs. These forms will have to be learned by heart, as if they were independent words. To make it easier, again, compose one sentence with each verb form.9.
Remember the cases. In Na'vi there are the cases, and though there are only a few of them, the rule number 8 also works here. Do not learn affixes separately, but the words. Try to create a sentence with each word in the ergative, genitive, dative, accusative.
10.
In the footsteps of the great. At the time of writing this, there were not many texts in Na'vi which could serve as an example of a proper use of the language. Don't let it stop you. Read the texts in the Corpus section, the letters from Paul Frommer which are authoritative sources. Memorize some useful phrases from those texts. Then it will be easier to use them as a whole in your speech, rather than cutting them in words. In your native language you speak also like this, because it's faster and more convenient.
Make a set of common phrases in Na'vi for yourself and remember them. And then you can easily use them in conversation with a few changes.
This compilation of the recommendations will change and grow. You can help other beginners to learn Na'vi when you try out these tips by your own and share your thoughts.