Always lock all doors and close windows, even if you’re going to be parked for a very short time. Never leave your car running while you run into a convenience store or go to an ATM. Park in a well-lighted area, and find a space near a store entrance or higher-traffic area, never in an outlying, deserted parking area. Park in attended lots whenever possible.
Don’t leave any valuables in the car. Keep any loose objects in the trunk or in storage bins under the seat. A blanket covering things can be an obvious invitation for a break-in. Minimize the number of small objects in your car — they’re great bait for thieves!
Parallel-park on main roads. Parking on visible major roads is safer than parking on side streets or alleys. If you’re parallel parking, park with the front wheels turned into the curb and the parking brake applied.
Choose an open, visible space.If you have a small car, try to avoid parking next to large trucks and SUVs, which give thieves good cover from security cameras and passers-by.
Never hide spare keys in or around the car. Experienced thieves know all the hiding places.
Don’t leave parking stubs in the car. It just makes it a little bit easier for thieves to be inconspicuous. Take them with you.
Get a locking gas cap. If your vehicle does not already have one, it helps prevent fuel siphoning and vandalism.
Don’t lock your glove box, and don’t keep valuables in it. If your car is broken into, a locked globe box can be an invitation for an annoyed petty thief to tear your dashboard up to get it open. Do not store your vehicle’s title in the glove compartment or anywhere else in the car.
Don’t park in the same place every day. Thieves will often plan ahead and wait for the right opportunity to come along.
Don’t ever think that your car is too old and worn to be a target. Casual thieves looking for property to steal might actually single your vehicle out, thinking it's less likely to have sophisticated anti-theft measures. Most often, stolen cars are stripped for parts rather than for resale, and the overall condition of the car makes little difference. High-tech alarm systems may thwart break-in attempts, but usually some damage results.
The best protection against thieves is to make your car unattractive to them in the first place.