First of the first, Italki is doing quite ok, although there are still some deficiency, for example it's at least not so convenient to do search, right? or I'm too dumb to find the good way? This platform has helped a lot of people, I am sure.

According to my feeling: italki, or other similar website, is like IKEA to teachers, and PanJiaYuan to learners. 

For teachers, or for Chinese study Chinese, there are still lots of issues not yet fully explained or described in Chinese, while as mother tongue users, it hard for us even to realize them, therefor, errors and some mistakes presented by foreigners, sometimes even the way they make the question  are truly treasures to us. Besides, when there is a different opinion raised to your work, don't get offended.

For Chinese learners, they normally can receive lot of answers to their questions or requirement, but unfortunately  answers are not always right, how to use them? First, don't swallow them right away, list them, by any means explicit to you. Then, rewrite your article, post again. By this repost, not only you should check whether  the directions are right or not, also you should check whether you had understood them right. It does cost you time and effort, but it can earns you ability and respect, it makes you a "worth to help" one.  

While asking for about grammar explanations, give the full context about the question point, for example, "她是漂亮", whether it's right depends on the context. “她喜欢跳舞，她是漂亮。”wrong. "她是漂亮，但她不太聪明，所以我对她不太感兴趣" right. That's why writing an article is a very good way to improve your Chinese. and note that questioning is a skill too.

Medium language(中介语) is very very helpful. It does not only enable teacher to make more accurate and comprehensive answer, but also help them to speculate the deeper reason to the problem and what need to be done. I suggested to lot of ppl here to attach English version after their Chinese write, because I had seen some misunderstanding or dubious corrections in replies. 

For students who is learning with a paid teacher or school, putting your teachers' work on you to here to check is more worthy than getting corrected work here and give to your teachers to get a good impression or a reference score. It's helpful for you to make a judgement about your cost, and it won't hinder you from getting your good score from your school.

Out of this platform, for those who does not learn for certificates, even you can't find Chinese material for study, start from your own interested material in your own language, use the translate softwares. But, feed them words or phrases, not sentences, because for Chinese - English(I only know them) translation, this way is more reliable, engineers has not yet solved all enigmas in them. From this, you can learn vocabularies, and figure out simple or basic grammar rules, because the formation of compound words and phrases contain patterns, in other word, grammar rules. Get a Chinese words dictionary（现代汉语词典）, to see the more detailed description for a word. The translation provided in text books are not reliable. After you learn a new word, categorize them, i.g. part of the sentence, about what, what is the emotion color, written or verbal ...

Learning a language can never be easy, so don't wast your time too much if not necessary, by necessary I mean you need them or you like them. But the thoughtful and diligent work will be paid back. Learning does not fail you.

For very beginners, of course PinYin is the first step, but i do suggest you to follow a teacher or look for a pleasant resource on web. There are few tricky points require some attention. 

Thank you for reading all this, and for putting up with my English.