If you end up getting in, you might already have a mentor on the faculty. If you already have a school in mind, check to see who the faculty are, and who teaches in your area of focus. If you can, find someone who knows the program better than you do. Ask questions not only about the quality of the program, but also about the politics involved. Be sure you know what you're getting into.
Some programs are internally very competitive for assistantships, PhD programs, etc.
Other programs are nurturing and collaborative, and students actually help each other out. Funding is also important. Find out your chances for an assistantship. Some programs offer lots of funding, others very little. Don't pick grad schools based solely on rankings.