Start by gathering information. Read this website carefully, meet with a pre-law advisor, attend pre-law events, and explore the Law School Admission Council (LSAC) website. Gathering information early will help you understand the time it takes simply to apply and to prepare for submitting an effective application.
It is also important to consider the cost of the application process and plan a strategy for saving whatever you need to cover LSAT preparation materials, LSAT registration fees, LSAC law-school reports, individual school application fees, and even the cost of traveling to visit schools that you are considering attending. Create a budget in advance. Information on fees can be found on LSAC.org and on individual school websites.