I want to get into MIT for post graduation. I still have four  years before I apply. Are there any things I can do in advance to start preparing for certain exams, so I can ensure I get in?

My two cents: Do internships at labs (not companies) at top universities. Try your best to have a couple of papers published (in international conferences, not crappy college techfest ones)/ GPA has to be very high, no question about that. To be safe, score well in the GRE and TOEFL too.

MIT is one of the best engineering schools in the United States and the world. It comprises of a huge vibrant & participative international community comprising of 9% student at undergraduate level and 38% at graduate level. Unfortunately, around 90% of students applying to get in are rejected. Even a stellar SAT score and a 4.0 GPA don't guarantee admission. MIT is essentially looking for super-students; being a super student, however, is achievable.So be precise with choices of your subjects and your grades ,B or B+ wont be working for you any more.You have to lift up your grades to A+ then only you are going to make your chances .Also, your SAT scores should be an average of 2220. For the 75% chance, your SAT score should 2350.