The proper way to wire a kill switch on a racecar with an alternator is widely discussed but the proper way is make or break in NHRA and IHRA legality and making sure the kill switch works properly.
The below diagram is the correct wiring of a kill switch with an EFI system so that the EFI system does not pickup noise and has clean power and ground for sensors/signals, while isolating the alternator from the kill switch for proper function.
Watch this Youtube Video for more info!