Sign up for a test date in advance so that you know exactly how much time you will have to study and prepare. Mark the date of your test on the calendar so that you won't forget. Determine exactly how many days you have to prepare.
Develop a strict schedule for preparing for the exam. If you only have one hour to study every day, then schedule one hour of study time. Make sure that you are dedicated to your schedule and never miss a study session.
Purchase a review textbook from the creators of the exam, the National Center for Competency Testing. The review textbook that they have available includes descriptions of the rules and practice questions so that you can head into the exam fully prepared.
Time yourself on the practice questions to ensure that you will have enough time to answer each question on the actual test. If you are moving through the problems a little slowly at first, that's okay. But you will need to pick up your speed as you get more comfortable with the information.
Study in a quiet place like the library if your home is very noisy and distracting. You will need to be fully focused when studying so that you retain the information.