Take practice tests. The best way to prepare for the test is to take previous tests and become familiar with the types and structure of questions you will be asked. Official practice tests can be purchased from the law school admission council or other websites, such as amazon.com. Keep time during each test section, and cut yourself off after 35 minutes, your limit during the actual exam. Replicating conditions similar to those that you will experience on test day is essential, so use pencils with erasers on your test form, and take some tests in public places like a library or study hall. Don't allow more than a couple minutes of rest between sections--during the real test you will have very little time to regroup between sections. As you take practice tests, keep track of your scores.
Work on problem sections. If you are unable to finish sections, practice reading more quickly and selecting answers faster. If you have difficulty with the analytical reasoning games, work out a system to set the problems up ahead of time. Many test takers swear by Powerscore's guides on the analytical reasoning and logical reasoning sections. Looking into these guides can be helpful.
Take more practice tests, and continue focusing on the section you did the worst on. Go over your answers and figure out why you got them wrong. You should start getting similar marks across all sections as you are putting the most effort in improving your worst sections. Your ultimate goal should be to complete every section before time runs out, while being able to thoughtfully consider and answer each question.