Consider Paid Parking
You probably go out of your way to find free parking on the street when you go to an event, but you should consider paying a few dollars to to park in a monitored lot. The security guards greatly improve the odds that your car will be protected.
Look For Light
Park in a well lit area that is easily visible from multiple directions. This light will cause thieves to think twice before breaking into your car, since they will be much more visible in doing it.
Spare Key Hiding Spot
A lot of people use magnetic hide-a-key compartments on their car, but as they grow in popularity, more and more people know about them. If a thief is able to find your spare key, he can easily steal your car without causing alarm. It's always best to keep your spare car key in your house.
Lock, Roll Up, And Hide
This is pretty obvious, but be sure you lock your doors and roll up your windows. And be sure that you hide any items in your car that may attract thieves in your glove compartment or under your seat.
Don't Keep Stuff In There
With all of the gadgets and devices that connect to cars these days, you have to be extra careful to take any valuables out of your car when you park. Remember to never leave your phone, iPad, GPS, laptop, or other high-price items laying out in plain sight in your car.
Locked doors are important, but thieves will expect that most of the cars they come across will be locked. To make sure your car is extra safe, get a steering wheel lock or brake lock to show them clearly that stealing your car will be very difficult.
Get a tracking service like LoJack or OnStar, and then be sure to get a sticker on your car that displays this. Knowing that the owner can track the car can deter thieves from trying to steal it in the first place.
Be sure that your car has the right alarm system for you. Loud alarms work great to scare off thieves, and some more advanced systems will even text you or call the police during an attempted theft.
Find A Center Spot
Parking in the middle of a parking lot may not be your first choice, but it is the best place to park to avoid your car being broken into. Not only does a car in the middle of the lot lengthen the getaway process, but thieves will also pass a bunch of other cars before getting to yours.
Don't Leave It Running
A lot of people will leave their car running if they are just going to run in somewhere for a few seconds. But it really only takes a few seconds for someone to jump into a running car and drive off. Be safe, and take the extra bit of time to turn off and lock your car every time you get out of it.