If you have not already taken one or more of the graduate school admission tests, enroll in a study prep course for the GMAT, GRE, LSAT or whatever standardized test relates to your chosen path of study. Many preparation options are available: classroom, online, self-directed workbooks and some that combine several of these options.
Your performance on these preparation tests will give you information about your readiness and help lead you to the programs and institutions that would be right for you.
Graduate school is a financial commitment. Can you afford graduate school? Do you want or can you get student loans? Will your current employer pay for or defray part or all of your tuition? Could you and would you move to a new employer that would help you pay for graduate school? You need to have some sense of what degree program you will study and where you want to go in order to estimate cost and establish a budget, should you make the ultimate decision to attend.
Are you able or willing to take a leave or quit your job for a full-time graduate program? If not, can you make the time in addition to your job responsibilities for class time, travel time and out-of-class work assignments for a part-time or executive program track? Find a program that fits both your content and time requirements. The difference between a 2-year commitment and a 7-year commitment is huge. Prod friends and family for insight into their experiences. If you can safely discuss your options with a trusted coworker, do so.
Family is an important consideration when considering graduate school because the time you would normally spend with your loved ones will no doubt shift to pursuing your graduate degree. In addition to tuition costs, there is a cost to you personally in terms of losing or reducing your personal downtime. You need to prepare your family or partner for managing the new time structure in the short term in order to meet the long-term goal. Everyone affected needs to understand the sacrifice and benefit in meeting that goal.
Some career tracks have identifiable markers where graduate degrees are required either implicitly or are the de facto standard. As a general rule, a graduate degree impresses employers on a resume and in hiring, but does not always translate into financial reward or upward mobility in every field. Look at your chosen or desired profession and evaluate the prevalence of people with graduate degrees at your desired level of work. How important are graduate degrees to the level of success you wish to achieve?