Simple. One of the best ways to get over the daunting prospect of doing past exams, is to break them into topics. Let's say you have 5 topics to revise for an exam. You can then print 3 exam papers, and skim over them - as you do, sort the exam questions into the 5 topic areas. Then, simply revise a topic, and do the select few questions on it that appeared in the exam. That way, by the time you're done revising your notes for an exam and you've covered all the topics, you also woudl've covered the entire exam.