If you have just one day in Memphis and want to maximize you touring, you can, with some planning, see three major attractions using their transportation.  If you drive to and park at the Rock 'n Soul Museum you can catch the 1030 Shuttle to Graceland (buy your tickets on line to avoid waiting in line).  You will arrive at Graceland approximately 1100.  Tour the mansion first off then leisurly see the rest of the exhibits , planning to catch the 1500 shuttle to Sun Studio.  You can take the tour of the studio with ample time to catch the 1715 shuttle back to the Rock 'n Soul Museum.  You arrive at 1715 and this museum is open till 1830.  It's a long but fulfilling day.