Here are a few of the things that you should do to prepare.
High academic proficiency:
You have to score high marks in class 10th, class 12th, and graduation.
Excellent CAT percentile:
A well-rounded profile:
Apart from these, you need a lot of mental strength. IIMA is known to be exhausting and wearying right in the first year. You just need to work hard and always be at the top of your game. This is going to be the only way to survive, grow and do well in your academics there.