Most test questions assign a percentage value which will be used by the instructor to combine all the components into a single grade. In an hour test period, you should calculate the number of minutes ideally available for answering the question. In this case it would be 24 minutes. Begin to outline the major points you wish to make. Of course, all this assumes that you have something to write with.
Some tests have instructions.
The number of students who are so primed to put down all the answers immediately and thus don't read the instructions are legion. Sometimes failure to read the instructions results in penalties, mistakes made in choosing questions to answer, or other problems not likely to endear you to the instructor. So read the instructions twice. The natural tendency upon receiving the question sheet is to find that first question and start it right away. It is possible that some of what you plan to put in your answer to the first question belongs instead to another answer later on.