The parallel setup as Minnflyer described is correct for a magneto kill switch. The series setup is correct if you have an electronic ignition setup.

In the parallel setup, EITHER switch by itself (closed) can kill the engine, but BOTH have to be open for the engine to run.

In a series setup, Either switch can also kill the engine by itself (open); the difference is that you're cutting off power to the ignition module when you open one switch, whereas on a magneto, you're grounding the current from the mag when you close the switch.