Obtain an application packet and financial aid packet from each school of interest. Ask for these forms at the same time as you request general information. Study the written materials and the application forms to learn the submission deadlines, prepare for the standardized tests e.g., GRE, GMAT, LSAT, you must take. Plan to take exams in the summer before your senior year. The scores will be good up to five years.
Most universities indicate the minimum score required for admission.
Reference letters are written by faculty who can comment on your undergraduate academic preparation and potential for success in graduate study as well as your commitment to the field. It is important but the relative importance is not easy to judge. Usually the more competitive the program the more value is placed on the essay. This can be a deciding factor in selecting between applicants who are otherwise equally competitive. The essay will be used to judge your motivation and commitment to the field.