After being rejected from MIT, and getting admission in UC Berkeley, I got to know where my shortcomings were. I might not have another chance to change it, but I can surely give you some pointers which might be useful for you.
Lastly, talk to the teachers as they can guide you thoroughly. Make your Statement of Purpose worthy enough. But always remember that MIT is not your only option. Do not get disappointed if you don't get admission there as there will be other options also.