IIM Eligibility

It's good to see your awareness and seriousness towards cracking a management entrance exam so early. Still, in the first year, there is ample time for you. You can start improving your vocabulary by reading good novels/books and newspapers daily(especially the editorial columns). Solving some good logical puzzles and related questions will also help in keeping your mind fit and sharp. Nothing much needed to do for Maths, as of now. just ensure your basic concepts are strong. 1-1.5 hours is quite sufficient to prepare for the time being.
One important thing, there is absolutely no need to start a full-fledged preparation for CAT(or any other entrance exam) now. Focus the next three years on both enjoying your college life and studying well; this phase will never come back in life so make the most of it. Ensure you score well in your exams(it will prove very helpful afterward) and try building your profile by participating in college's extracurricular activities, certification courses or an internship if possible during vacations, social work, etc). Your profile will help you get that edge over others. All the best!

The Indian Institutes of Management (IIMs) are a group of 20 public, autonomous institutes of management education and research in India. They primarily offer post postgraduate, doctoral and executive education programmes. Admission for residents of India to the flagship two-year PGP programmes at all IIMs is based on the Common Admission Test (CAT).
CAT is national-level MBA entrance examination conducted by one of the IIM on rotational basis. Admission to IIMs is two stage process. First stage is based on CAT score. Candidates who clear CAT are called for GDPI. Selection is based on CAT score, GDPI performance and acedmic records. The minimum eligibility criterion for admission in MBA is at least a 3-years Bachelor's degree in any subject from a recognised university with at least 50 per cent marks or equivalent (45 per cent for SC/ST or persons with disability (PWD) category).CAT test does not have predefined syllabus. CAT tests candidates in general aptitude including Verbal Ability (English), Quantitative Ability (Mathematics), Logical Reasoning (LR) and Data Interpretation (DI) skills. CAT is multiple-choice based test with penalties for wrong answers.
Admission in IIMs after CAT is based on following criteria:
GDPI Call: 70% weightage will be given to the scores of CAT and 30% weightage to the Application Rating Score (Xth marks, XIIth marks, Graduation Marks)
Final Selection: Group Discussion: 10%, Personal Interview: 40%, weightage to the Composite Score at the final stage of selection to arrive at the Aggregate Score: 50%
Weightage vary in different IIMs.