First of all, I think try to improve the vocabulary is the most important step to have the improvement of English. Because to use a high-level or subject-specific vocabulary can show the audience that the writer have a high-level language skills.
To memorize more and more vocabularies by reading books. It's most easiest and the most fast way to memorize. Do not memorize the dictionary, it's hard and will forget very fast and completely. Secondly, grammar is the hardest section for the people who's first language is not English. There are 12 tenses to learn. Do grammar exercises is a way to get the improvement.
Also people need to study the grammar by talking with other people. Write more and more paragraphs by using different tenses and ask teacher for help to fix the grammar errors. Last but no least, when the writer should have a logical organization of your ideas. A good paragraph writing form can help the writer organize his/her ideas.
Further, write a outline before the final draft, and the ideas should be write from least important to most important or least specific to most specific.
