Speak with your graduate school's adviser to see if your school offers any Ph.D. help for students. Your school may offer grants for specific departments, there may be assistance from alumni or your adviser may know of some private contributors. Your school may have a Ph.D. program that funds students who do research and teaching at the university.
Fill out your Free Application for Federal Student Aid, or FAFSA. Use this application to apply for loans. If you are not considering a loan, most schools will still require that you complete this form so that they can consider you for any type of financial aid.
Research special programs in your field, as there may be grants offered specifically for those opportunities. There may be special fellowships or research grants in your field of study.
Research grants that are available for any special populations. For instance, there are grants for minorities and women. There are grants offered to many different types of students, so you may qualify for one or more.
Complete any applications, and wait for the decisions to arrive.