Ignoring Institute's Study Material and Practice Manual by relying blindly on reference books you are putting more effort to cover some irrelevant topics that are not required for examination. The Institutes material is a bible for scoring exemption in all subjects at IPCC.
Not revising within 24 hours. It doesn't matter how much you study, if you aren't revising it within 24 hours of first learning then be ready to forget. The course is vast. Do revise within half an hour in the morning whatever you read last day. Blindly taking coaching classes of all subjects from best teachers in the town. Join classes where tests are conducted regularly and marks are assessed in a good manner. Everything is easy in IPCC. You can study almost everything by your own, but you may feel losing the writing skill which you had in school days. Not tracking daily progress. Take a sheet of paper and pin it on your study board. Now write whatever topic you covered in a day on that sheet so that it could be revised after net 10 days, 30 days or 90 days.
Wasting a day completely not studying. It doesn't matter how exhausted you feel, never leave a day blank without studying. Go through Costing or Finance theory lying on your bed in an hour or so but just do it. Solving more than one book. You need not kiss every book available in market. Do all numerical of one book completely. Maintain a notebook of solutions to all questions. Not learning section numbers and standard numbers in Tax, Law and Auditing. If you are not sure of section/standard numbers then do not quote them in exam.
Better to learn them thoroughly to have an edge over other students. Not attempting entire paper during exam due to lack of time or selective studying. When you attempt entire paper you increase chances of scoring. It is better to solve a 16 marks question in 5 minutes roughly rather than attempting a 6 marks question completely in IPCC paper.
Sitting at the last bench during class lectures. This is not your typical college lecture where you can sit at the last row and scroll through Whatsapp notifications. Sitting on the front row makes you proactive and you are compelled to focus even on theory subjects like ITSM. Not clearing doubts arising in conceptual subjects.
ASK YOUR TEACHER. ASK. ASK. We lose inquisitiveness after school or CPT exams. The doubts that breed in initial stage stay with you till the end. So, ask whatever concept is not clear.
Disclaimer: These are my personal observations. Feel free to disagree.