Lock it up.
Take a moment to ensure that your car doors are locked, and that all windows and your sunroof are closed. And don't ever leave a spare key hidden in or on your car; thieves know where to look.
Hide your valuables.
Don't puff.
Make your car less attractive to car thieves.
Invest in a steering wheel lock.
Or maybe some floorboard locks.
Or how about a gearshift lock?
And you can always put a boot on it.
Hood locks protect your car and look cool.
Armored collars are just for warriors.
Get a car alarm and use it.
Audio alarms are good. They are loud and attract attention when unwanted parties try to access your vehicle through the door, hood, or trunk.