This is not a level playing field. Preparation will vary from person to person. Each individual should devise a plan that best suits his or her own personality. There is also no particular major course of study that guarantees admission and law schools do not require a pre-law course of study before admitting someone. Hence, a Fine Arts major has the same chance of being admitted as a Political Science major.
Law schools look to the difficulty of all courses taken when evaluating applicants.
A person who performed well in more difficult courses will likely be admitted before someone who performed well in less difficult courses. Once you have decided to attend law school, you should approach the remainder of your college career with an eye toward law school. Take as many courses that develop writing and analytical skills as possible. Take pre-law courses if they are offered because, it won't hurt to get an introduction to the subject matter that you will be studying for the next three years. The most important thing is to take courses that develop the skills.