Personally I would not advocate all-night revision sessions. In fact, I'd suggest exactly the opposite, lack of sleep makes it impossible to concentrate. In addition to plenty of sleep, if you find nothing is sinking in, take time out to relax - go for a walk, go out for some lunch, see a film, go for a drink with some friends. Figure out what time of day you concentrate best (for me it's in the morning), and try to do most of your studying then. Make sure you eat properly. Drink plenty of water. Exercise, go for a run or to the gym, play a game of squash or whatever.