Make sure you know the practical details about your exam
Where will it be held?
What time does it start, and when do you need to get there?
If you have to travel some distance, what time will you need to leave?
What do you need to take with you?
Also make sure that you know what to do if something goes wrong. You might, for example, be ill on the day, or get held up on the journey, and you need to know who to contact.