Read the task carefully
Do not rush reading the task, even though you are under pressure to finish the writing exam in one hour. Read every word carefully and underline key words. Think carefully what the topic is about and what the question is asking you to say about the topic.

Planning
The planning stage should also not be rushed. You should spend at least 5 minutes planning your essay. You need to make sure that you have strong main ideas and a good structure for your essay. This will enable you to focus on the topic and question. Also, if you make an effective plan, this can actually speed up the writing of your essay. This is because a lot of time can be wasted when writing if you need to think of what you are going to say. The plan can reduce the time spent trying to think of what to say when writing. Essentially, it’s more time efficient to do all the thinking at the start, in the planning stage, in order to reduce the time spent thinking during writing. Learn more about planning.

Developing strong main ideas
A lot of my students tell me they struggle to come up with good ideas. My main suggestion is to practice this. Look at lots of sample questions and think how you would answer them. You may get lucky and get one of these questions in your exam! As well as this, brainstorming in English is a skill and if you practice it you will get better at it.

Developing your ideas well
A grade six requires responding to all parts of the question. A grade seven and above requires that you extend and support your ideas. This can be done by supporting your main ideas with explanations, details, and examples. For more on this see the section on writing the body of the essay.

Use an appropriate structure
To get a high score it is essential that you structure your ideas well. This is because the examiner will be able to see the quality of your ideas if they are structured well.
Learn more about essay structures.

Useful Links on my site:
Questions and model answers
The three main Types of essays

From the ebook: Essay Writing Task 2. By Mike Wattie

Available here: https://www.ieltsanswers.com/ielts-books-task2-essays.html