The ideal month to take the LSAT is JUNE. Which JUNE? The JUNE that is fourteen or fifteen months before you plan to enter law school. In particular, for someone graduating college in four years and intending to attend law school just after graduation (in the Fall), the ideal time to take the LSAT is the JUNE at the end of the junior year. The LSAT test score (available three weeks after the test is taien) is required to do an efficient job of selecting apropriate law schools and to submit a complete application. Consider these words of advice from Anne Richard, Associate Dean of Admissions and Financial Aid, for George Washington University Law School: "The time to submit the application is when it is done and in the best shape possible but, earlier is better, because I believe most law schools have a rolling admissions process [applicants are accepted on an ongoing basis]". LINK
The four tests of the law school application cycle:
June : Optimum test date for an applicant intending to submit an early law school application in order to possibly benefit from rollling admission (with rolling admission, the admission process is done on an ongoing basis). If there is a problem with the June LSAT (you were unable to take the LSAT, you did poorly on the LSAT, etc.), you can conveniently take or retake the LSAT in September/October.
September/October: A September/October LSAT may be more appropriate for an applicant attending the Summer Semester or Spring Quarter, or working full time at a summer job. Still possible to submit an applications early. The big downside of taking the LSAT in September/October is that a retake would be in December.
December: The December LSAT may conflict with fall finals. May face a more competitive review at law schools that use rolling admission.
February: By the time LSAT scores have been received, many application deadlines will have passed.
