The most important thing to remember in the writing test is your audience. On the tasks it often says thing like “write a report for a university lecturer” but in fact it should say “write a report for an examiner who will look carefully for mistakes & problems”. Most people think too much about the “whole” task and don’t pay enough attention to the actual sentences they write or the words they use. Your answer is basically comprised of sentences so you should concentrate on producing a series of “good quality sentences” instead of “an answer”. It is a good idea to work on key structures such as “conditionals” or subordinate clauses and get into the habit of producing these in your writing.
There is a tendency to “overcomplicate” answers by including too much information. It is a good idea to keep your answers as simple as possible in task 2. A good approach to task 2 is to take 3 separate ideas that are directly relevant to the question and to develop these ideas using good sentences & vocabulary.
It is very important that you answer the question fully. For example if a question asks “What problems does X cause and how can be these problems be solved?”, you must offer BOTH solutions and problems in your answer.
There is no right or wrong answers the writing test but it is important to keep YOUR answer relevant to the question. If you include ideas / sentences that are not directly relevant to the question you will lose marks.