Just remember to read the question carefully, underline keywords if you have to. Spend an hour or so tonight looking at mark schemes from previous years to find out what key words the examiner is looking for. Also, don't hesitate when answering the question, just take your time, I remember when I sat my biology paper for a-levels, I have more than enough time. Like I said in a previous post, all you can do is go in the exam room with a positive mind and just try your hardest.