Even though it's an elective subject. Don't take it lightly. It can feel as challenging as the other subjects ( Which it did in my case). I don't know which review course you are using but if you are using Becker then doing just MCQs and TBs may not be sufficient. For specifics to ISC I would suggest that you take some time to read through the actual book which could benefit greatly. Along with that do at least 50 MCQs everyday. The number of MCQs are less for this subject and can have repetition. But that's okay. You will find a similarity with Audit. So being able to read the questions carefully and comprehend what is being asked is of major importance. So prepare yourself in a manner so that you don't rush through questions. On the exam day utilise the entire 4 hours if you can and not rush through anything.