I’m a B Tech CSE 2nd year student What should I do to bag a winter internship at IIM Ahmedabad?

Usually, IIMs have research internship programs.The preparation would depend on what field you want to work in. Ideally, to get an internship at IIM Ahmedabad or any other elite institute, you should start looking for professors and start applying. 

Your CV shortlisting would mostly depend on how well-known your undergraduate institution is, what other experiences you’ve had etc. Start preparing with the trickiest part which is writing a Cover letter and always take help from your professors at college. Start sending out your CV and Cover letter to all the professors you wish to work with and you need to start this procedure 1-2 months before your winter breaks. The usual time to get a reply is a week and you’ll be briefed about the further process in the email. 

Remember, it is likely that they assign you some clerical work like collecting articles related to their ongoing research or may send you to interact with NGOs to collect data. Although the experience will help in the future, If you want something more substantial like assisting professors and actually giving your input for their research work you might have to do the extra task and get a reference from your college.