This world is - Dar-ul-Asbaab, i.e. is one of cause of and effect. Hence, the key to success is hard work and thorough revision. A Muslim student will be no different from a non-Muslim student in this regard.
After making adequate preparations, a Muslim student will place his trust in Allah (SWT) and seek His assistance instead of relying solely on his/her preparation.
The sunnah procedure is to perform Salaat-ul-Haajah and recite the masnoon duaa supplicating to Allah (SWT) for success.
As for actual duaas before the exam paper, there are no prescribed duaas or surats.
One may recite the following:-
(1) Start with reciting Bismillah-ir-Rahmaan-ir-Raheem. (2) Recite Ya Fattaah seven times. Al-Fattah being an attribute of Allah (SWT) meaning the 'One who provides the opening'. (i.e. Seeking Allah's assistance to open up one's mind in order to answer questions with ease and perfection.) (3) Reciting Durood upon Rasulullah (sallallahu alaihi wa sallam).
