Coupling Nut mounted shaped punches should have a keyway to ensure a positive alignment both to the machine and to the work. The accompanying die should have a spot to align it with the punch. The shape of the keyway is determined by the machine manufacture. If no keyway is present, then follow the manufactures' directions.
The most common keyways are:
Round Keyway
Square Keyway
V-groove Keyway
Relative position of keyways to die on shaped punches
Optionally, tooling can be ordered with 2 keyways/spots, the second being at 90 degrees from the first. This literally doubles the punch's return on your dollar.