Hi, as a student qualified for IPM and currently studying in IIM Indore, I feel like I have enough credibility to give you some good tips-

1. Thoroughly prepare English and Mathematics under a timed environment- learn to efficiently practice 20 subjective maths questions in 40 minutes etc.

2. Buy guide books like Arihant's IPM preparation book and practice everyday for 3-4 hours minimum. In order to get the maximum questions right quickly, you need to have a good practice set of questions. So, practice from this book, and most importantly, some previous year's papers.

3. As far as online platform is concerned, go for whichever you like ( Careerlauncher is a decent choice), but ensure that the above two points are adequately covered by them. Ultimately, you are the one who needs to put all the effort and hardwork.

For more details, check out this link-

https://bschool.careers360.com/articles/ipmat

All the best!