With experience as a parent, a teacher and a perennial student, my three top tips.
Short bursts of intensive concentration (20 minutes) are worth more than an hour of letting your mind wander.
Concentration means reprocessing important material by diagrams, bullet points or some other form of thinking about it. (Refer back to the syllabus or defining material for what's important.)
Winding down the night before an exam is important. Don't reread the notes late into the night. It doesn't help, and it ups the panic level an drops the alertness. A good night's sleep is the best preparation. I used to tell my students that I had taken many, many exams in my life and never - no, not once! - had I ever learned anything the night before that helped me in any way. (And I nearly missed one once by being so tired that I didn't hear the alarm!)