Start by knowing the right syllabus. To draw a clear cut preparation plan for the entrance exam, it is important to have knowledge of the IIMC syllabus. The right books and study material are good assets to help crack the IIMC entrance exam. While the newspapers are good sources for current affairs and events. Some books you can refer are:
1.Popular Master Guide for Journalism & Mass Communication Entrance Examination by R Gupta
2. Handbook of Mass Communication (Theory and Practice)-V K Joshi
3.Mass Communication Journalism Entrance Examination of All Indian Universities-Arihant
A significant aspect of preparation for IIMC entrance exam is to learn from the mistakes made during the course of preparation.and while solving papers. The trick is to understand where it went wrong and how to rectify it.
You can refer the entire syllabus and past papers on the following site: https://media.careers360.com/articles/iimc-entrance-exam
Hope this helps!