Use common sense. Lock your doors and remove your keys from the ignition. Close your windows completely and park in well-lit areas. Don't leave valuables in your vehicle, especially if they can be seen from outside the vehicle. Never leave your car running and unattended. Use a visible or audible warning device such as an alarm or steering wheel lock, brake lock, or window etching or Micro Dot marking to indicate to would-be thieves that your vehicle is protected.
Install a vehicle immobilizing system or device such as smart keys, fuse cut-offs, kill switches, starter or ignition disablers, or wireless ignition authentication.
Equip your vehicle with a tracking system that emits a signal to the police or monitoring service when the vehicle is reported stolen. Some systems employ “telematics” which combine GPS and wireless technologies to allow remote monitoring of a vehicle. If the vehicle is moved, the system will alert the owner and the vehicle can be tracked by computer. Be sure you understand how a company plans to use and protect your personal data before purchasing their product.