IIM

Basically, there are 3 sections in CAT exam - verbal ability, DILR, Quants.
Verbal ability-
Start reading newspaper daily to increase your reading speed and grasping power. Don't miss out the editorial page. Do proper analysis of articles on editorial page. Try to make summary of articles that you read para by para. However, reading newspaper won't be sufficient. Start solving RCs on a regular basis with proper analysis.
DILR-
This is one of the toughest section especially from previous 2-3 years. Not only it is tough but it also checks how quick your senses are and how good you are in selecting the sets. Therefore, the best thing to score in LR-DI is to practice more questions on daily basis so you understand which sets you should leave and before attempting the sets what are the things you should look for.
QUANTS-
This section is one of the most scoring section for student and you too should try to get maximum mark in this section. It has a proper syllabus and you need to practice each and every chapter. The major topics are- Geometry, Arithmetic, Algebra, Number System and Modern Math. It is basically the math that you have studied till tenth standard. However, having said that, the questions are not really easy. Focus more on Arithmetic and Algebra as these two are most important topics. Start with basics then go for intermediate.