Prepare for the Law School Admission Test, or LSAT. You can do this online (see References) or by studying resource material available in book stores. Practice tests are also available online.
Sign up for the Credential Assembly Service (CAS). Nearly all law schools require this. It's a transcript-verifying, law school recommendation service that you take part in to prove your eligibility to attend. You can find a link to this in References.
Take the LSAT. You will need your passing score to apply to law schools. You can register for it online (see Resources) or call 212-968-1001. Tests must be taken by December to qualify for the following year, though some schools request that you take the test earlier. A few schools allow a late test to be taken in February.
Study law schools and choose the ones you want to apply to. Each school will have different application dates and processes, so carefully examine the requirements of each and follow its guidelines.