CAT

Hi Sparsh,
90th percentile is not that difficult a target to achieve. Based on last year's paper, if a student had attempted ~25 questions in Verbal, ~12 in DILR and ~20 in Quant, he/she would have scored 90th percentile in each. With good preparation of fundamentals and rigorous practice, this is a very achievable target. I am going to jot down a few critical things to keep in mind while preparing.
Prepare from basics - No fancy shortcuts and gimmicks
Try to take some coaching from nearby CAT coaching centres. They will help you a lot in preparation.
Read. A. Lot.
Solve gazillion questions to build stamina and speed
Keep at it. There will be times when something else takes precedence. Grit past these times and keeping coming back to CAT preparation.
Grasp of basic arithmetic, a well-honed reading habit and lots of mocks - this combo can easily take you to 90th.
If you are preparing with any level of seriousness, shoot for 95th percentile at least. That is also a very achievable target.
Best wishes for CAT preparation

The eligibility criteria of IIM-A for PGP programme is a Bachelor degree with minimum 50% of marks for general and 45% for reserved categories from a recognised University. Selection process : The selection of the candidates for admission in PGP programme at IIMA is a two-step process. The candidates are short-listed for Analytical Writing Test (AWT) and Personal Interview (PI) from among the candidates who have a valid CAT score. The CAT sectional cutoff is 70 for each section, while the overall cutoff is 80 percentile for general candidate. So you have to first complete your graduation with at least 50% of marks than appear in CAT exam and obtained very high percentile above 98 for selection in IIM-A.