How do you secure your motorcycle against being used without permission?

You answered correctly. To prevent unauthorized use of your motorcycle, you should always remove the ignition key and engage the steering lock. These two actions make it much harder for someone to start and ride away with your bike. Disconnecting the battery, as in answer 3, is not a common or practical security method for preventing theft or unauthorized use, and is not required by German traffic regulations. Remember: always use the key and steering lock whenever you leave your motorcycle unattended.