You could use a timetable to mark out revision times for each subject and then stick to it.  Another great way to stop procrastinating and get started is to use the Pomodoro technique: this is as simple as setting a timer.  For example, set your timer for 50 minutes.  This should be concentrated study time – no distractions.  At the end of 50 minutes you have earned yourself a 10 minute break – time for a quick walk or a cup of tea.  Then go for another 50 minutes of concentrated study.  Remember to make your goals for each day realistic, and reward yourself for achieving them. You’ve earnt it!