Most schools will arrange for you to visit the campus, have an interview with an admissions officer, and get a guided tour of the campus. The interviewer may ask about your scholastic standing, courses, and extracurricular activities. Interviews are generally not required for state-supported schools except in special circumstances. While colleges offer a wide variety of majors, not all colleges and universities offer the same type of major. For example, in New Mexico, one university offers the only architecture degree in the state.
Schools also differ as to the level of degree program offered.
Astronomy at one school may be an undergraduate program while it is a graduate program at another school. The degree of academic competitiveness is all-important. College work should be challenging, but it should not completely overwhelm you. Consider living in a college dormitory. Some people prefer the sense of community and togetherness among faculty, students, and administration that is characteristic of a small college, and the sense of being known and of making an individual impression.