What training is emphasized? Sure, you're applying to a graduate program in your field, likely a subfield within the discipline you studied as your college major, but graduate programs offer training in specific specialties (or "sub-sub-" fields). For example, an applicant may major in Psychology and apply to a graduate program in the subfield of Developmental Psychology, but he or she needs to know more about the graduate program. Specifically, in what areas do faculty conduct research? If you are interested in, say gerontology, but none of the faculty study it, you're not likely to get the training you desire. Some graduate programs explicitly state training emphases. Others don't. In these cases you have to do your homework to make educated guesses. Look at faculty research interests and the research labs within the department. These will offer important clues as to what to expect from your training.
Some graduate programs emphasize theory and basic research. Others emphasize application, conducting and applying research findings to solve problems and influence policy. Know the difference because if you tell a theory-oriented graduate programs you're interested in applied research you'll get an immediate rejection letter. Not to mention, if your interests don't match the program you'll be miserable should you be admitted.
Curriculum and Coursework
Most graduate programs list the curriculum and course list. Do the classes look interesting? Do the course requirements look like they will fit your training needs?
Doctoral programs require dissertations for graduation, but the form the dissertation takes can vary across disciplines. Can you locate any information about the dissertation requirements? Is it an empirical dissertation? Is it instead a lengthy literature review and theoretical paper?
Is the university and program accredited by the relevant governing bodies? All US universities must be accredited by a regional accreditation association. At the program level there is a great deal of variation. Discipline-level accreditation is common in applied fields such as social work, nursing, applied psychology, and business. Quality programs in these disciplines must be accredited by the major disciplinary body. Note that graduates of unaccredited programs may find it difficult to land jobs and sit for certification and licensure exams. This is a very important step in determining whether to apply to a graduate program.
Graduate study is an expensive endeavor, but the cost per year can vary dramatically from $10,000 to $40,000 depending on institution. Can you stomach the bill? Is it worth it?
Sources of Financial Aid
Most institutions have multiple sources of financial aid. In addition to federal aid, universities have other forms of aid, such as scholarships and tuition remission in which the student does not have to pay tuition. Universities often have work study programs in which students earn some of their tuition or cash for working on campus. Graduate departments offer other funding opportunities in the form of research and teaching assistantships.
Faculty are the heart of a graduate program, especially a doctoral program. As a doctoral student research is your world. It's important to work with faculty whose work you find interesting. Many applicants choose a graduate program because they wish to work with a specific faculty member. Don't focus only on only one professor because the most prominent faculty often are very busy with large labs filled with students and may not take new students each year. Have multiple faculty in mind to increase your odds of acceptance but also to ensure that you get the training you desire.
What resources do the university and department have? If your field is highly specialized, will you have access to the equipment you need? Is there lab space in the department? Does it look like graduate students have their own lab space? If you will need special equipment, does it look like the department has access? Will you be able to achieve your goals, given the program and university's resources?
Not all graduate programs are ranked, but any ranking information from sources such as US News is helpful.
How selective is the program? Peterson's Guide (http://www.petersons.com/graduate-schools.aspx) provides basic information about programs, including statistics on how many applicants are accepted each year. What are your odds?
If you're applying you obviously know where the graduate program is, as in what city or town, but what do you actually know about the place? Is it a town? City? How large a city? Do you know enough to determine that it might be someplace you would like to live for a few years?