Go to the DMV and pick up a copy of your state's driver's manual. They should be readily available among the various forms and other educational materials at your local DMV office.
Take your driver's manual home and read it cover to cover. Have a couple of different color highlighters available to highlight relevant information. Try to only highlight the most important information or things you're afraid you wouldn't remember otherwise. If you go crazy and over-highlight, nothing will stand out to you and that defeats the whole purpose.
Study the manual with a licensed parent or a friend that is also preparing for the test. Take turns quizzing each other, making a note of any missed answers.
Take a great driver's test quiz on the Progressive Insurance website. Enter your zip code for a driving test quiz based on the questions on your state's driving test. You can choose between a 20-question quiz or a more complete 100-question quiz.
Read through your manual again before the big test. Pay special attention to any of the questions you missed while studying with friends or taking the online driving test quiz.