Every institute has its own criteria for the admission process. Most of the B-schools consider CAT scores.
In the case of IIM’s, IIM A and IIM C consider CAT scores and give weightage to CAT score only. But IIM B along with a good CAT score prefers your 10th, 12th, and graduation performance along with your work experience and the kind of work experience that you have.
To get into top B-schools you need to strengthen your profile with various kinds of social and extracurricular activities that you have participated in the schools and college. You also need to perform well in your WAT and personal interview. You should provide proper and logical reasoning for your answers.
For more details, you should check the websites of these institutes and keep checking the previous year’s cutoffs.