First of all, my most important advice is to be really strict with your timing. In any exam you should allocate your time to be commensurate with the available marks. This is a two hour exam, and two parts are worth roughly equaly marks. Therefore you should spend an hour on each. Part A has four questions - therefore you should spend 15 minutes on each question. Even if you know a lot about one of those topics, it is crazy to spend more time on that because the maximum number of marks that you could get for any one question is 12. Even if you put down 50 correct points about GIF files, you would still only get 12 marks for that question. The essay in part B is worth over half of the marks for the exam, so make sure that you spend the full hour on that question.