Try to remember parts of the exam that you did not feel very comfortable with when you took it the first time. There may have been a certain category of questions you did not do well on. Perhaps the clinical part of the exam caused you some nervousness that resulted in your making mistakes.
Brush up on the exam material. Review practice exam materials and books. Also take practice tests on line that will help refresh your memory of what kinds of questions are on the exam. (See Resource 1.) Spend extra time reviewing those parts.
Register for the exam again. Each state has a different type of exam, so make sure you prepare for the particular exam given in your state.
Get as much rest as possible the night before the exam. Eat a good meal the morning of the exam, and avoid cramming any more studying in at the last minute.