It is strongly recommended that an applicant planning to take the LSAT give ample time to preparation. Two or three months is generally the minimum amount of preparation time an applicant should plan on devoting in preparation for taking the test. Don't forget that everyone else taking the test has most likely prepared and not to do so puts an individual at a distinct disadvantage given that the final score is partially predicated on the results obtained by the other test takers.
A candidate's LSAT score is reported as a "Scaled Score" and next to it the "Percent Scoring below that score". Therefore one is not simply completing a test as well as possible, but also competing against all other test takers in terms of the "percentile" ranking aspect.
Look at LSAT Sample Score Percentiles
To prepare for the LSAT, a candidate may obtain/purchase commercial materials (booklets, pamphlets, etc) easily available through bookstores, on-line, or numerous other similar venues, or obtain previous LSAT (with answers) which LSAC makes available for a fee (please see their website for more information), or enroll for more formal instruction via private organization that specialize in preparing students for the test. Among them a candidate might consider investigating the following (although this does absolutely not constitute a comprehensive list):