Win a gold cup in all races to unlock the Special Cup circuit.
Get 100 coins or more by the end of the cup to unlock extra tracks. Press L or R to view and play them. Once you get an "A" rank on every cup in every class you will unlock all of the original tracks from Super Mario Kart.
Successfully complete all circuits in all classes to change the background color of the title screen.
At the character selection screen, press L to shoot a green shell or press R to jump.
During a race, press Select to use the horn.
Just before the last light turns on during the pre-race countdown, press Gas to get a quick start.
Hold L + R + B + Start and power on the system to delete the current saved data.