Learn as much as you can about the format of the test. If you have the opportunity to ask questions about the test in advance, determine what the time limit is, how many questions will be asked, whether or not there is a wrong answer penalty and whether or not you will be penalized for unanswered questions.
Find two to three practice logic tests. You can find these tests online, or purchase hard copies in many bookstores (check the SAT and standardized testing sections). The specific content of the tests you obtain is not critically important, since logic tests are designed to require no external knowledge.
Work through the practice tests, with a particular emphasis on timing. Abstract reasoning test questions are designed to be solved in an average of 25-35 seconds. Remember that because test questions typically progress from easier to more difficult, it's better to budget slightly less time for the first 20 to 30 questions. Keep a clock or stopwatch handy as you complete each test to keep track of your time.