Make certain that your car is functioning in good mechanical order and always drive on no less than a quarter tank full of gas. Your windows and doors should be locked immediately once you are in the vehicle.
In parking lots, be aware: look around you, look into your car, at the passenger side floor, and in the back seat. Check under the car as well. If you are parked next to a big van, enter your car from the passenger door. Some assailants attack their victims by pulling them into their vans while the women are attempting to get into their cars. Look at the car parked on the driver's side of your vehicle, and the passenger side. If a male is sitting alone in the seat nearest your car, you may want to walk back into the mall, or work, and get a police or security officer to walk you back out.
Consider using a deterrent device such as the "Club", steering wheel column sleeve, alarm, or starter interrupt switch.
Don't leave the garage door opener on the visor or anywhere in the open. Thieves look for openers when they steal cars so they can commit an easy burglary as well.
Don't leave valuables in your car. Park your car in the garage.