read --> write --> correct --> repeat

Accordingly , if you want to learn to write academically there are resources for that , but if you're looking for regular writing then I suggest movies with English subtitles,books and articles.

As for me, I would watch movies and read novels. The more I watch and read, the more I am used to the grammar. And while I do that, I also learn the basic grammar. So I understand. 

Not only for writing  , but also for overall improvement ,you must expose yourself to english constantly .Moreover when you listen sonething download written script also,then read while watching the same thing and then written , it is very useful