If you want to work on improving your academic writing skills, here are four of my suggestions:
Make time to read the news, magazines, books, blogs – anything you read is going to help you!
Practice writing any time you have some free time in your daily activities – on the bus, on the train, etc.
Keep Growing Your Vocabulary
Make time to add new words to your vocabulary journal every week.
Take a class, or find a teacher/tutor to give you individual help
Free activities on the internet are great, but what can help you even more is a teacher who will give you personalized guidance and feedback on your writing skills.