Lock Your Doors
A majority of car break-ins and thefts are from unlocked cars. Even if you are parked in front of your house, in your driveway or inside your garage, lock your doors. Criminals like to walk down the street and see if a car is unlocked, if it is they open the door and take whatever is visible and move on to the next target. However, if the door is locked, they are more likely to move on.
Secure Your Vehicle
Roll your car windows up all the way and engage the car alarm, but do not depend on it as the only way to deter a thief. A car thief can break into your car and be out in about 30 seconds, fast enough that an alarm doesn't scare most of them away.
Keep Your Vehicle Tidy
Thieves like to window shop! Avoid leaving anything visible in the car. Almost any item that's visible from the outside - even if you think it is worthless - could be seen as valuable to a thief. Your spare change, sunglasses, even an empty bag (a thief may think there is something inside the bag) could be valuable in the mind of a thief.
Conceal All Proof
Stow your electronics and accessories well out of sight, or just take it along with you. The proof alone might be enough to pique the interest of thieves, including items such as power cords, adapters, and GPS windshield suction-cup mounts. If you remove the suction cup, make sure to wipe the ring off the windshield; it's a dead giveaway that you own a GPS.
Stash Before You Park
Get in the habit of putting items you want hidden in the trunk of your car before you arrive at your destination. Thieves will linger in busy parking lots looking for you to stash your valuable items.
Park in a busy, well-lit area and avoid concealment from larger vehicles, fences, or foliage. Avoid parking in isolated and poorly-lit areas.
If you see a break-in in progress, call 911 immediately! Provide the 911 dispatcher with as much information as possible, such as:
Location - Provide an address, block number, or specific location in a parking lot.
Description of the suspect - Provide as much information as you can, i.e. sex, race, age, height, weight, hair color and length, color and length of facial hair, colors and style of clothing, and identifying marks such as tattoos and piercings.
Direction - If the suspect flees, give the direction of travel. If they flee on a bicycle or in a vehicle, describe the color, make, model, and license plate number, if it is safe to do so!