A “hook” is what I call a very particular attribute of your high school experience or background that separates you from most or all other applicants to any school. Colleges like to accept students with hooks in order to create a diverse freshman class.
If you are a recruited athlete, your athletic ability is your hook. Colleges also reserve spots for minority students and legacy students, who have parents or other relatives that are alumni of the institution. Additionally, some colleges hold a few spots for what they call “development cases,” whose families contribute significant amounts of money to the school each year.
For the above categories, you do not have much control. That is to say, you will either fall into one of those categories or not. However, there are many other ways to enhance your application and stand out from the larger applicant crowd. Colleges are looking for students who will positively contribute to their schools and communities, and if you have done that in high school, you need to highlight that on your application. For example, how did you make an impact on your favorite club? What new policies did you institute?
My biggest suggestion to improve your chances in admissions is to always be authentically you. If you like to make jewelry or paint landscapes, why not approach local businesses to see if they'd be willing to give you some space within which to sell your work? If your hobby is playing the piano, why not enter some contests in high school and try to obtain regional, local or national recognition? If that’s not for you, though, do not force yourself to play simply because you think it will help you for college. The truth is, there are no guarantees in college admissions—no matter what hook you may have. I firmly believe that your authenticity will resonate with admissions counselors. Regardless of the outcome, if you honor yourself and your likes and dislikes throughout high school and the college process, it will be so much easier for you to love the journey.