I don’t know what you need to do to get into schools like MIT or Stanford, but what I think is MORE important is what you do while you are at whatever college you get into. Getting into and graduating from MIT is not a free pass into the “life of your dreams”, but it probably does make the way a little easier. There are plenty of good engineering schools out there, so don’t be disappointed if you don’t get into one of the top 10.
What can you do now? Decide on something you’re interested in learning about and start to read about it. If you’re interested in designing a web application try creating a simple web application. If you’re interested in mobile apps, write an iPhone app. There are tutorials on the web (google can you help you find almost anything! Try “iphone app tutorial”) that can teach you how to write simple applications and many times the compilers you need are free if you’re a student. There’s nothing like practical experience to point out the things that interest you. If you’re interested in computer security, read about hacking and what needs to be done to prevent hackers from getting into a system. Choose a project, join a club at school, ask a teacher at your school to help you with a project, or even to suggest a project.
I don’t know if you need to be good at coding/programming NOW to get into a software engineering program at a university, but certainly, if you want to pursue a career in software engineering, you have to like to program. It’s a lot of fun when you can get things to work. This field is constantly presenting new challenges and changes and “paradigm shifts”. You’ll never be bored if you don’t want to be.
Bottom line: to make yourself a more attractive candidate for any university you need : good grades, good SAT/ACT scores and a background that shows that you are a person that likes to learn and achieve. Do as well as you can on your grades and SATs, and then get involved in all sorts of extracurricular activities. LOTS of them. Be active in them. But don’t just do it to make yourself attractive to colleges, do it because you want to learn and make yourself a better person.