Once you have a fairly clear idea about what advanced degree you wish to pursue, you can begin to make a timeline as to how you are going to complete the many tasks associated with putting together a competitive application.
However, please remember that this is not always a linear process. You might start out thinking you want to be a teacher and then, as you continue to explore and find out the requirements or what kinds of positions are available if you obtain a credential, you may find that an MSW is more useful. Or you may start out thinking you want to work in public policy only to find out that a joint degree that includes an MS in environmental science will give you the expertise that you need and make you more employable. Exploring various programs will help you understand their distinctions and differences in terms of pre-requisites and the curriculum offered. You will also need to familiarize yourself with the tests you need to take and if there is either a stated or implicit pre-professional requirement. And you will want to start talking with professors and supervisors who know your work and are available to write you excellent recommendations.
Many things can shift your thinking about your future. You may find the costs of some graduate school programs prohibitive or be stretched to consider a program in another state because of the curriculum or particular expertise of one of the professors. Taking time to explore options and continuing to talk with graduate students, professors and professionals will help guide you in the direction you want to go. You may discover you will be a more viable candidate if you take a year to work or decide that the test score you received necessitates you to re-take an important required exam. Narrowing your focus to a particular area of study and/or program is progress towards your ultimate goal of applying to graduate school but you still have many decisions to consider.
Once you have assembled a possible list of programs you will want to organize them into a visual document that helps you easily see requirements in terms of essays, deadlines and required tests. This will help you compare programs and also allow you see overlaps in the types of essays that are required, when applications are due and how much each will cost. Some programs do have fee waivers for application fees or make exceptions for certain populations and the list can also help you see what kind of funds you will need in order to apply. The number of programs you apply to will depend somewhat on the kind of degree you are applying for, but three to five is a reasonable number for most PhD and Masters students. (The healthcare field has very different application protocols and applicants in these fields often apply to many more). If you are applying for a PhD or Masters degree, applying to multiple programs often gives you options and also some negotiating power for funding if you are accepted to more than one program. Many graduate school application deadlines are in the fall with some extending into the following spring, and some programs have priority and general deadlines. Medical school and other advanced degrees in the healthcare field have their own schedule.