What can I do to improve my chances of getting into an Ivy League school?

One thing you can do to improve your odds is to apply to **all** the Ivies.  It's a numbers game at some point.  There are X number of competitive spots and Y*X number of equally qualified applicants.  Essentially, buying more lottery tickets, if you're qualified, increases your odds. I read an interesting bit about getting into top-tier schools.  It went something like this: "You're in a grocery store to buy 10 oranges.  The orange display has 1,000 oranges in it.  950 of these oranges would be perfectly acceptable for your orange selection criteria but you only need 10.  You pick 10, put them in your basket, and pretend you rank ordered them." The upshot is, there are more kids who are equally qualified than there are available positions.  Improve your odds if you meet the requirements by applying to more schools.

Standardized test scores hold a lot of students back from admission to an Ivy. Make sure you aren't one of them. Sign up for the PSATs if your school doesn't offer them. I took the PSATs twice, the SATs twice, an ACT prep test once, and the ACTs once. My score went up each time. Practice makes perfect. You should familiarize yourself with standardized testing formats and question patterns. Get some SAT vocabulary flash cards. If you are getting below 2000 (200 psat) on the SATs or 30 on the ACT, you need a tutor to keep your Ivy hopes realistic. Anything lower than that will be a serious liability.

Woah! You're just a Sophomore and you've got so impressive stuffs to show. That's truly incredible! So you've got three years to go. Great. So as to ensure an admission in an IVY school, you've more than sufficient time left. First of all, lets talk about ECs. You said you're not so much into sports. Never mind. You must be having some other hobby right? Like music, or something similar. Do as well as you can in them. Don't be just 'ordinary' in them. Do something that clearly doesn't seems ordinary. Take an year of time and prepare hard for Standardized tests. Firstly, identify whether you're an ACT guy or a SAT guy. Then take any one of them(though taking both of them is not a bad idea). TOEFL is the easiest thing you should find. Then take the SAT Subject tests. They're pretty easy, if you're comfortable with CBSE/ISC.  If you will, take Advanced Placement tests (better when you're in 12th). Try writing essays and enhance your English skills. Then you may like to indulge in some cultural experience by going to remote areas for Educational purpose like teaching English, etc. Plus, you must do some amount of Community service. If you haven't done any yet, get started now. Start taking leadership initiatives. And keep doing the 'extraordinary' things in the field that captivates you the most, that is, Computer Science. This can really impress the Admission officers. At last, be a good person and keep up your character. Hope that helps! : ) Cheers!

You would obviously need exceptional grades in either your bachelor's degree, related work experience, relevant research, and recommendations from people who matter. Keep your options open by applying to several schools. See this list of the http://bitly.com/1tAKBG1.