Preparing for the BJCP exams (Tasting or Written) is a classic example of “practicing how you intend to play the game.” For the Tasting, you do need a firm basis in style knowledge, but the majority of exam scoring is based on your descriptions, feedback, and quality of communications back to the entrant on each scoresheet you complete.  All the Written questions are published, but time is short, so you must prepare all your answers to every possible question in advance so during the exam you are just unloading your prepared answers.  There is no time to ponder what you should write.