It's Simple, Really
Short Answer: Great grades and maturity. Detailed Answer: 1. Great grades. 2. Strong academic classes, including AP and honors (Ivies want to see that you have exhausted your coursework at your high school and achieved consistent excellence). 3. Maturity. If you have done poorly in a semester or two, admissions officers want to see you take responsibility for it without placing blame on various people or situations. 4. They want to see that you have not sacrificed your grades for too many extracurriculars. 5. They want to see that you have settled on one or two extracurricular interests and have pursued leadership opportunities. 6. Excellent writing and thinking skills. The fact is, anyone’s Mom can write the essay, and it can be just as readily purchased off the Internet. So admissions may or may not formally count the SAT writing score in the application process, but they will definitely take note of how well you did. 7. They want to see that you followed their instructions.