I'll share my strategy for this particular subject
What i do is
I have a book of Muhammad Sohail Bhatti...
I read a specific topic
then search for it in google
then I give a look to past papers... and try to cover all aspects which appeared in past papers..
Forexample
Muhammad Bin Qasim (711-715)
-Read from the book
-Do research on internet about the Headings given in book
-Try to make notes or atleast keypoints
-Look in the past papers
-try to cover the aspects given in paper
and that makes one perfect topic for the paper