Another thing which I have observed among some of the aspirants, while preparing for the exam; is that they mostly consult "Exploring the World of English", which , per see, doesn't fulfil all our text book requirements. This book doesn't contain anything exhaustive on important things like voice, phrasal verbs and even idioms. Most of the idioms in this book draw their basic etymology from the antiquity-based myths and incidents, like: Pyrrhic victory, penelope's web and the stuff, and not all encompassing.
In addition, one needs to be in possession of the original versions of a couple of internationally recognised lexicons, like Oxford and Chambers; for these dictionaries give one a much deeprer insight into the grammatical intricacies than the locally published grammars; not least the example sentences which show us the correct usage of words and phrases.
Rest I do agree with bro s bhaloo,Dr Junaid, Dr farrukh and imperturable over their observations.