You should investigate class sizes, ensembles available, and applied opportunities. In some areas of music the choice of a school may boil down to the applied teacher, or the choral director, or some other specific attraction. Some schools have applied lessons taught by a faculty member while some depend heavily on graduate assistants to teach undergrads. Ask questions about the faculty members. This may mean proper practice rooms, music library, technology lab, to mention only a few.
Most schools have some kind of track record which is known in the profession.
Talk with people who know the industry. This may include your guidance counselor, your high school music teacher, and professionals in the area. When you have drawn up your short list of schools, plan visits to each to learn more about it. This will give you an opportunity to meet the faculty and sit in on classes or lessons. You should also plan such trips so as to be able to hear performances by appropriate ensembles.