The catalogs and web sites will also list faculty members and areas of study. Write, call or e-mail the directors and faculty members of programs that interest you. Try to get to know as much as possible about the departments and professors. Don't ask them about information provided in the catalog or on their web site. During this research phase, start looking for a mentor.
Mentors are invaluable as advisors in academics, research and departmental politics.
You want to choose someone with tenure, to be sure that person will still be teaching there when you arrive. It will only cause you and your recommenders headaches to wait until the last minute. Decide whether or not you want to waive your right to see the letters, i.e., whether you want to give the writer freedom to say what they like about you if you trust them, whether you question what they say will be flattering, or other considerations. Tutors often take their time writing these letters, so allow for that time. Provide them with pre-addressed stamped envelopes, reference forms, and a general description of the programs to which you are applying.