Going to graduate school is a big commitment. Getting a PhD in the United States generally takes at least 5 years, and the national average is closer to 7 years. Unlike undergraduate studies, your professors and fellow students may one day be your peers, especially if you plan on going into academia. As a result, it is important to carefully consider where your research would best be supported.
Some things you might consider when choosing a school include:
Before choosing which programs to apply to, you should consider what kind of philosopher you are. Are you interested in more historical figures? If so, from what area and time period? Are you interested in a particular "school" of thought, or just specific figures? Or are you more interested in topics/areas of philosophy, rather than individual philosophers and their works?
It is generally helpful to discuss these matters with peers and professors/mentors who know you well. Professors may also be able to suggest programs they feel would be a good fit for you.
More broadly, there are a few sites that can help you narrow down your search for graduate programs. Be sure to use your own judgment and check the department pages themselves as information on these sites can be out of date or misleading (e.g. a professor specializes in "Phenomenology," but only teaches one figure from that tradition, or has not taught a graduate seminar on that topic in 5+ years; checking CVs and course catalogs can be helpful in this area).
Note that one can find "rankings" of graduate schools and it may be tempting to simply only apply to "the best programs." This is not a good idea. Just because a school does well in terms of faculty publications, placement, etc. does not mean it will be a good fit for you or your interests. The APA has released a statement on graduate school rankings; SPEP has also released a statement. That said, such lists can be helpful in terms of finding a place to start when researching schools. See, for example: