I follow a pattern. Trust me this works during exams, I call this the ultimate cram. wake up the day b4 the exam, if u have a day spare right, and chuck a 2 hour study lot, then break for 30 mins, the 1 and a half hour block, break 30 mins and again 1:30, break and from there on as many 1 hour slots u can get in. By the end of the day you've successfully covered 7 hours of revision. The key is in the unwind. When u unwind dont think about the exam tomoro. Just forget it, and I strongly re-inforce rific's post. This is for those times when u'r under a critical stress load... you'll have 5 of them all up, half yrlies, yearlies, half yearlies, trials, then the big mofo lol