For colleges, selecting a freshmen class is a lot like betting on horses. As anyone who’s spent time at a racetrack will tell you, it’s hard to pick the winners. A horse can have the best trainers, the right physical attributes, and a 26-pound jockey who can get a horse to deal blackjack, but still come in dead last.
When a college accepts you, they're betting that you will perform well over the next four years. High grades, good test scores, and successes in your high school activities indicate that you have the potential to do well in college. But much like horse racing, there’s no guarantee that you will actually live up to those expectations once you get to college and the race starts. It helps your case if the college can sense you weren't someone who made all your decisions based on what you thought would please colleges.
The best way to show colleges that you're a safe bet is to be authentic in your pursuits. Seek out the subjects that really interest you. Pursue activities you really enjoy. Make an impact. Leave a legacy. Challenge yourself. Gracefully accept your failures and move on productively. And most importantly, be who you want to be–a quarterback, a math nerd, a trombone player, someone who watches foreign films nobody else likes, a poet, a budding physicist, an interpretive dancer, or some bizarre combination of those things–just be authentic. Base your decisions on the person you aspire to be, rather than on the perceived preferences of a college you aspire to attend.
You can't fake character traits like passion, curiosity, character, persistence, humility. That's why those students are such good bets.