WHAT CAN YOU DO TO EXCEL AT IT?
Be aware of grammar. Think about grammar. Notice the aspects of English grammar that are the same as or very similar to those in your language. If you notice grammar similarities and differences, you will probably learn the rules more quickly.
http://www.usingenglish.com/quizzes/ includes a series of quizzes to help you learn different grammar contents. Just scan through the beginner contents and choose the one you need to practice most.