Some people don't agree with me, but I think you need to know what you want to study before you head off to university. It saves time and money. Changing your major can delay your degree and cost you a fortune. It's best to know what you want first.
An interest in continuing your education is the first place to start. It is not uncommon for someone to go to university and not know what he or she wants to study, but if you have a sincere desire to learn, that will be enough to get you going.
You have to have an interest in learning and improving yourself. As others have stated a wide variety of interests is best as it gives you more opportunities. You have to be open to new people and ideas. A lot of students get hung up on they don't know what to do with their lives, sometimes the first couple years of college studies is what it takes to figure that out.
You should have an interest in a learning new things, an interest in acquiring knowledge in subjects that intrigue you, an interest in meeting new people and learning new things about yourself and others, and an interest in figuring out how to live on your own.
Your interests need to be broad and ultimately should be about self improvement. Your interests will likely develop into what will ultimately be your major course of study, so it is important to at least start to think about what subjects interest you so that you can investigate colleges with an eye to what programs they offer and what different universities can offer. The best schools provide opportunities for their students to explore all of their interests.
University is a place where students have fun and do all kinds of interesting and enlightening things. As the post above suggests, a student with a variety of interests is more likely to be accepted. Once there, though, it's important for a student to sustain other kinds of interests. Studying and preparing for the career you've chosen; learning what it takes to be a good citizen in a dormitory or sorority; participating in clubs and organizations in which you're interested; taking advantage of the academic and cultural activities on campus.
Doing any or all of these things will make the university experience, one of the the first significant investments of your life, both more rewarding and valuable.
As far as I am concerned, there are no particular interests that you need in order to be admitted to a university. It is best if you have a variety of interests if you hope to be admitted to a very selective university, but there are no particular ones that are required.
The selective universities (at least in the United States) want to see students demonstrate a range of interests. They do not like to see students who only care about one thing. A student who gets admitted might, for example, be interested in music, in sports, and in some other sort of outside hobby. The universities are just looking for people who will be interesting and will enrich the university's campus.
Universities are filled with people who have extremely diverse goals and aspirations. The education process is lifelong and stepping into the college world is just one aspect of this journey. One very important aspect of college is the fact that learning from others can be key in broadening our horizons with other cultures and ways of thinking.