Plan exam day timing and materials.
Exam morning is best planned backwards from the start time. Subtracting the early arrival buffer gives your target arrival, subtracting travel gives your departure, and subtracting the morning routine gives the wake-up time. Taking one more step back by the sleep you want produces the bedtime, which is the decision actually made the night before and the one most often got wrong.
Backward schedule
Arrive = exam start - early buffer; leave = arrive - travel; wake = leave - morning routine
Bedtime
Bedtime = wake time - sleep hours x 60
Twenty to thirty minutes is usually right — enough to find the room, settle and use the toilet, without so long that waiting builds anxiety. Add more if the venue is unfamiliar.
Almost always. Sleep loss degrades recall, working memory and reading speed, which costs more marks in a three-hour exam than an extra hour of late revision typically adds.