Here are some of the impressive tips to enhance English:
Increase your vocabulary.
Try to write Rich English, by using effective and impressive words, which are quite tough and beyond your mates understanding.
Use quotes and sayings. You can use Instagram or Tumblr to get good quotes, there are many such pages which have got English content of a high level. That would help you a lot!
Use your creativity to answer. Don't mug up things which your teacher make you to write, rather answer on your own. As the teachers get bored off reading the same answer which she taught over and over again. So even you miss out something in your answer she wouldn't mind as you've written something unique.
Make sure that you begin and end the answer in a very emphasizing way! It going to get you bonus marks!