How do I prepare for IIM, Indore IPM on my drop year?

It is preferable if you enroll in any educational coaching institution because you are taking a drop year, especially for IPM preparation. This is because for IPM, students have to give a PI and an Aptitude Test.

• The classes would be well-versed in giving CAT and IPMAT foundation courses which can be considered an additional benefit. 
• Also, you will not be familiar with the format of IPMAT unless you attempt a mock test before the final exam. 
• IPMAT is online, there won't be any previous year question bank, therefore the mock tests will offer you an advantage and also assist you for the PI round involved in the selection process.
• For the Quantitative aptitude section, I would suggest that you refer to NCERT questions (Classes 11th and 12th) and several competitive examinations questions.. 
• For the verbal aptitude test, You should focus on improving your basic grammar, reading books, and improving your vocabulary. 

Lastly, as I have seen my friends prepare and do well in exams, I will encourage you to do the same. Be confident while giving your answers and attend the PI with complete honesty.