Firstly, prepare a topic thoroughly,mentioned in the syllabus. Once you have a grip on the topic then go through the past 10 years papers and solve the queries on that specific topic only ( For example first Prepare "Astronomy" and then go through the past 10 years papers and solve the question and mcq's which are from this topic). I bet about 80% of your papers will already be prepared and what else be missing, you will prepare.
Best of Luck