From NSW Police online - a news story about a car jacking in Sydney's west (see link below)
What can you do to help reduce the risk of being car jacked.
1. If you are returning to your car in a car park especially at night take the time to look around, if you see something suspicious listen to that voice in your head, walk away, call Police and/or wait and observe.
2. When you get to your car after you activate the keyless entry (central locking) or use the key the old fashioned way, look inside the car to ensure that no one is waiting inside your car. When you do this stand beside the back door so that it can't be opened.
3. When you get in your car lock the doors.
4. Drive away if you see or suspect trouble.
5. Keep your car doors locked at all times.
6. Do not place valuables such as laptops, wallets or bags on the front seat where they are visible.
7, At service stations after filling your car, lock the doors when you go to pay.
8. Avoid driving though areas that are known to be high crime areas, especially at night.
By following these simple steps you may reduce the likelihood that you will be car jacked.
Link to story on NSW Police online