Hi Yailynne: I may not be the best person to answer your question because I did not initially get into a prestigious, elite, high-end college. I eventually transferred into an elite college -- the University of Southern California -- by proving my academic worth, character, initiative, and desire at a community college and a state university.
But, to answer your question, what high end, elite colleges are looking for is an incredible SAT Score, your grade point average in high school, and if you took rigorous/ challenging classes in High school including a large portfolio of AP classes. (I did not have a high SAT - I scored a lousy 840 out of 1600; I had a good GPA at 3.5: and I did not take any AP classes.)
Some colleges will also consider your extra curricular activities such as were you Senior Class President (I was), excelled at sports (I kind of did), have other special talents like music or acting, internships or unique work experience, or how you addressed and overcame certain obstacles in your life.
Every college has difference admission standards. Some colleges rely solely on Grades and SAT. Other colleges are looking at a much broader view of the overall student to ensure a diverse and well-rounded student body.
As I mentioned, I did not get into my "Dream School" -- University of Southern California -- initially. But, USC told me exactly what steps I needed to take at the Community College and State College that I attended in my freshman and sophomore years so I could be admitted in my Junior year as a transfer into USC.
USC was excellent at giving me Feedback on the steps I needed to take to be accepted as a "Trojan."
Hope this information helps.