I was a fellow IGCSE student a few years back. I know what you are going through trying to get those A*s. I spent a considerable amount of time making good study guides written by a student for a student. I think these guides may be the answer to some of your problems. Have a look at my website. Apart from more information about the books, I have also put up some study tips and links to free resources which were a big help to me. There is also a list of keywords which I think you should remember for the exam. Good Luck.
http://sites.google.com/site/thethinkseries/