Normally these aren't printed at all. This is above all a matter of communication with the service bureau/printing people, not with a forum.
One of several solutions is to apply a spot color to them, which has a special name.
Like Monika says, use a special spot colour for dielines.
Have these on a separate top layer and set them to Overprint.
That way you can easily turn the layer on and off and the overprint means that even though the dieline layer is visible and printable it will not affect the stuff on the other layers.
Europe, Middle East and Africa