i try to sleep all день if i want stay calm ...i am just kiding .....well Ты can do some exercise или yoga for about 15 min ...in this way Ты can relax and remember everything better .......you can also eat some honey или Шоколад i think that this is help too
during exams, i always have my lucky ring on and of course a Конфеты beside me, it helps me to relax... Ты want a tip? well my advice.. ^^ sit beside your smartest classmate.. then, there's nothing to worry about =) hehehehe