The first step is to create a basic checklist which can be used for any of these types of questions. This could include a few grammar tenses and structures, a few versatile bits of vocabulary, and some points to cover within your answer, such as opinions and justifications.Next would be to prepare some points for each topic covered in the syllabus which can be adapted to different questions by only making basic changes - this way you can go into the exam confident that you always have a starting point.