An advice, though as basic as it is, yet everyone neglects, is to have a complete grasp of the syllabus of the subject that you will be examined on. It is fundamental for you to have complete knowledge regarding the main content and exam structure for you to be fully equipped during exam day and sit your exam in top form.
Other than that, I would say, diligence, perseverance and motivation, after all, whether you succeed, to a certain extent is dependent upon your efforts. However, vital it would be, for you to derive your own study techniques and exam strategies. Find out what study technique works best for you and work smart, for a proper study technique would be like a catalyst and saves you from unnecessary efforts.
After you are fully equipped, do your best and forget the rest, for faith and confidence in yourself would elevate you to higher grounds. Cheers!