Im currently a sophomore in high school and I’m a VERY dedicated student. I work hard and get good results. I take all my classes in IB except for math. I also have a bunch of EC’s like student leadership, free the children, peer support and many more. In what ways can I prepare for next year in terms of applications and SATS {I am a canadian student}? Thank you so much! 
There is NO way to “ensure” you get into any of the highly selective and desirable colleges.
You cannot “ensure” acceptance into a school that has a 6.3% acceptance rate. You could do every right and still be rejected. Acceptance into Ivy League schools is even harder for international students.
Please read this thread. Although it’s about MIT, everything in it applies to Yale: http://mitadmissions.org/blogs/entry/applying_sideways