How can I do well in exams?
Rest early the previous night.
For a multiple choice paper, first step through the questions answering the ones you are confident of without spending too much time on any one question. For this first pass through don't bother to guess. Then go back to the beginning of the paper and go through the questions you were not sure about. Just work through it as if you are doing a job. According to the way that the multiple choice answers are scored it will probably be worth guessing answers on the questions you don't know the answer to.
For a non-multiple choice paper you may have questions that ask you to describe a concept you have been taught and then apply it to a particular example. Note that with these sort of questions usually the bulk of the mark will be on the application of the concept rather than the definition. Take each question one at a time and attempt to complete it. If you find yourself getting stuck, then move onto another question.
If you have a choice of essay type questions then briefly skim read all of the questions to decide which is/are best for you to take on, then really focus on one question at a time. If the paper requests that you answer more than one question then try to divide your time well so that you have enough time per question.
Try mindful breathing just before the exam starts and/or during the exam.
I used to teach my students the art of mindful breathing before exams start. Its a Buddhist meditation technique, but is applicable to anyone and you don't need to be a Buddhist to gain the benefits.
You simply, close your eyes, concentrate on the tip of your nose where the air flows in and out, and watch your breath. Keep doing this and if your mind wanders, gently bring it back to your breath and the tip of your nose. Studies have demonstrated that what this does, even for 5 minutes, is to dis-engage your sympathetic nervous system (anxiety produced during a stressful situation) and engages your parasympathetic system, which calms you down after a stressful event.
Once the exam starts, you will find that you are more calm and can focus better on doing well. If its a long exam, you can even take a mindful breathing break after an hour or so - or when you start to get stressed out again. Even a few minutes will help and it might make the difference in how you finish the exam.
I have had a lot of feedback from students that this really helped them - worth a try!