To add to what preply has already stated, one of the easiest parts to improve on is your essay. If you can raise your essay 2 points you will greatly improve your writing score.
Always be sure to answer the question posed, do not use the prompt as an excuse to write about something you want to. This is not a Presidential Debate, you must answer the question.
Clearly state your thesis, agreeing or disagreeing with the prompt at the end of the intro paragraph and stick to it.
Provide one counter argument. If you are arguing for the importance of telling the truth to your friends at all times, provide an example of why others might disagree, then, and this is important, disprove the counter argument.
Sum up your points and restate your proved thesis