You have studied hard, therefore the subjects are in your head.
Relaxation and good cheer will bring it out during the exams.
Tiredness, anxiety and nervourness will cause mental block, and
remembering the answers only when you in the bus going, home after
the exams.
Therefore have a good night's sleep the night before the exams.
Get up early, get your exam paraphernalia (prepared the night
before), go the exam venue early. Relax. Muster all the
keypoints you can. There is nothing else you can do to save
yourself. Be a bit playful to be relaxed.
Oh yeah. If you want to take energy boosters, like Red Bull,
take it 45 mins or at least 30 mins before the exams start.
Alcohol, an absolute no no.