You should take the LSAT no later than the summer or fall of the year in which you intend to apply, a full year (or more) before you intend to begin law school. If you are still in college and plan to go to law school right after graduation, you should take the LSAT in June after your junior year or September/October of your senior year.
If you take the test in June and are still in college, remember that you will have a number of other demands on your time through mid-May, all of which will compete with your LSAT test preparation. This is especially true if you are graduating that May—e.g., finals, graduation, moving, etc. On the other hand, if you take the September/October test, you will be balancing the tail end of your preparation with the beginning of the semester. Some students, however, prefer the fall date because their minds are more attuned to intellectual matters, they are less tired than at the end of the semester, and they are less distracted by summer’s work or play. Judge the best time for yourself based on what you know about your own schedule and mind, your test taking skills, and your work habits.
You should not wait until December or February of your Senior year (or the year before you attend law school) to take the LSAT. You will not know your test scores when you have to decide to which schools you will apply. Also, most schools have rolling admissions which means they start accepting students as soon as they receive completed applications. The later you take the test, the later you will submit your application, and the fewer seats there are in the law school class for which you can compete. Some schools do not accept February test scores for that fall’s admission.
There are some other differences in the test timings which might be meaningful to some applicants: The February test is always “nondisclosed,” meaning you will not receive your corrected answers back when you receive your score. The June test is the only one that is an afternoon sitting—Monday afternoon, instead of Saturday morning. Finally, note that if you’re still in school, the December test falls right during (or just before) final exams.
If you are still in college but planning to take some time off before applying to law school, you can take the test whenever you’d like up until the deadlines above. LSAT scores are good for five years.
The deadline for registration for the LSAT is usually about a month before the actual test. Register early in order to secure your preferred test site.