Challenge Yourself

Constantly challenge and stretch yourself to the limits. Exposing yourself to formal and informal English (written and oral) will be advantageous for you can never be sure of the manner of communications of the people you'll get to meet in your line of business. You do not have to be very literal and memorize every sentence or get to know the definition of all the words. The mere fact that you comprehend what you read is good enough and to be able to explain it and state your opinion about the topic is even much better.