Well, do you know IELTS Liz? She's very good in explaining it all! Otherwise, I'd say don't write under the word limit and make sure you answer all parts of the question. But, I want to say that we're of Danish nationality, and here you learn English from you're 8 years old. Basically everyone speaks it fluently. Also, it was my boyfriend who took the test, and I'm a native Canadian, so I could tutor him too. So that might have made it quite a bit easier for us. We didn't really put that much effort into writing. I'd ask someone who worked their way up from a low score to a high score, I think might be more helpful to you.