Focus on increasing your grade point average before you graduate. The grade point average is one important indicator of "success" that admission officers highly weigh during the admissions process. Essentially, the higher your grade point average is the better your chances are in impressing the admission officers. But, if you haven't done really well in undergrad, show that you have been successful in other aspects of your life (such as stellar work experience or graduate level work already completed). Also, some admission officers will consider as positive a "rise" in your undergrad grade point average during the last 60 or so units.
Take the LSAT. Your LSAT score is extremely important to law school admission officers, especially at the elite law schools. Moreover, a higher LSAT score, depending on the law school you apply, can calculate into scholarship dollars that will go directly to reducing the cost of tuition. Doing well on the LSAT generally requires practice and preparation. You can take the test "cold" but your best approach will be to either take a prep course, self-study using actual past exams and/or private tutoring way before the actual test date. Go to the Law School Admission Council's website to review test dates, deadlines and to register for the exam. The sooner you begin planning the better.
Get your previous professors to write you a stellar "letter of recommendation." The sooner you begin the process of getting to know your professor, the easier it will be for them to write a genuine "letter of recommendation." Additionally, consider that the most compelling letters will be tailored to a specific law school, as opposed to a general recommendation letter, so if you are not planning on applying to a large number of schools, ask your professors to tailor their letters according to the law school you are applying to. Keep in mind that an admission officer might read hundreds of "letters" every admission cycle, so the more "genuine" a letter is, chances are, the more persuasive and convincing the letter will be. As far as number of letters, each law school is different but the number generally ranges from one to three. For example, as of May 18, 2010, Harvard Law School considers two. But check with the law school you are applying to because each law school has different requirements.
Write your personal statement. If you are interested in a particular law school visit its website to get more information on what essay topics are appropriate. While it is possible to use the same essay for more than one law school, this all depends on which schools you apply to. For example, Pepperdine School of Law requires two essays: a personal statement and an essay response to the University's mission so check with the particular school you are interested in.
Apply to law school. Now that you have finished the LSAT, gotten your professors to write you stellar letters of recommendation, completed your personal statement and if you are in your last year of school have almost finished undergrad its time to apply.