The preparation for USMLE step 2 CS and the CCS subcomponent of the step 3 is different from the other exams. You won't need to read and memorize tons if information to be prepared for this exam, if you have good basis in clinical knowledge from medical school or during preparation for the other USMLE components then you are in good shape to take these exams. For both exams you will need to know at least the most common differential diagnosis for each chief complain. You also must learn the exam format and practice continuously until you feel comfortable with it.