I know reading the title you will look at this saying .... Wow
this is soooo pointless but! If you have ever played WII tennis that serves it that way it is so irritable! I have mspent the past 2 months working it all out as google tells you nothing! Now....
Step 1Use the A button to throw the ball up instead of flicking the controller
Step 2Before hitting the A button have the remote in the serve position
Step 3As soon as hitting the A button quickly do a short, quick serve motion.
If all goes well congrats! ::.Dont get frustrated if you dont get it just keep trying.::