Very few people achieve their full potential on the LSAT without some preparation.
At a minimum, you should take a practice test, including the writing sample, under actual time constraints. This will help you estimate how much time you can afford to spend on each question, as well as which question types you should spend additional time practicing.
Familiarize yourself with the test instructions and question types. The test format should not delay or distract you from answering the test questions.
Most law school applicants also study test-taking techniques and strategies. The free materials below are a good place to start.
Free Official Prep Materials
Test Prep Videos
Do your best on the LSAT with these test-taking tips, straight from LSAC's Test Development Group.