Arcade version:
Hold A + C + Start on controller two after the title screen appears.

Arcade operator mode:
Hold X + Y + Z + Start at the title screen. This will allow the difficulty level and credits to be adjusted.

Shadow mode:
Hold L + R + A + C + Y at the title screen, then press Start to display the options menu. "Shadow Mode" and "M Stick Adjust" options will appear on the menu.