Nov. 20, 2013 -- intro: Every 43 seconds, a car is stolen in the United States, which is close to a million vehicles per year.
Former car thief Steve Fuller was himself convicted six times for stealing cars. Hundreds of other times, Fuller said, he was able to successfully get away with it.
"I stole cars because I was on drugs, and I needed the money," Fuller told ABC News' "20/20." But once he kicked the habit, he kicked the crime too.
So now, in an effort to try to make up for some of the damage he did, Fuller agreed to give up the "trade secrets," what car thieves know that we don't. His tips could deter thieves and keep your car safe.
While some advice might seem obvious, such as not leaving your car running with the keys in the ignition, Fuller revealed what most car owners don't know, but car thieves do. By knowing what car owners don't, thieves can often boost a car in less than 10 seconds.
Check out these seven tips that could mean the difference between holding onto your car and having to walk everywhere.
quicklist: 1title: Your Car Model Might Already Make It a Targettext: Honda, Toyota, Acura, and General Motors vehicles were some of Fuller's favorite cars to steal.
"They're easier to steal," Fuller said. "They have good resale value so the parts are in demand. It's as simple as that."
In fact, the top two most stolen cars in the United States last year were Honda Civics and Honda Accords, according to the National Insurance Crime Bureau.
quicklist: 2title: It Matters Where You Park Your Cartext: Car thieves avoid cars parked in front of houses and in driveways because they're too wide open and visible.
Dark secluded locations, such as apartment buildings and complexes, carports, underground parking, and parking garages, can be appealing to car thieves because they can have their pick of vehicles in one location.
"I liked it because it's quiet. I can hear if somebody was coming," Fuller said. "All I really have to deal with was somebody coming down from their apartment to get in their vehicle, and at that time in the middle of night it's not usually that often."
quicklist: 3title: Car Thieves Dislike 5 Things: Daytime, Kill Switches, Alarms, Nosy Neighbors and Security Camerastext: Being quick and inconspicuous is necessary when stealing a car. That's why car thieves avoid things that may call attention to themselves.
This means stealing cars at a certain time. Fuller said he preferred to come back between 2 a.m. and 5 a.m., because most people are asleep. "It's nice and quiet, less distractions, less people walking around," he said.
Having a kill switch in your car can also deter thieves. Kill switches disrupt the flow of electricity at the battery or ignition or disable the fuel pump. If well hidden, kill switches may take a while to deactivate and can deter car thieves who don't want to waste time and will move on to another car.
Good alarms with motion sensors, nosy neighbors, and security cameras also deter car thieves, who will simply go to other areas where they can avoid those certain things.
quicklist: 4title: You Should Reconsider Leaving Your Car Runningtext:While it might seem like a great idea to warm your car up in the morning, you might as well put a bow on your car. Car thieves will simply hop in the car, put it in drive, and go.
Police also warn that leaving your keys in your car at a gas station, even while you are pumping gas, is an invitation to have your car stolen.
quicklist: 5title: Don't Keep Spare Keys in Your Cartext: Think you've got a great hiding spot for your spare keys? Car thieves know where to look.
"Glove compartment, center console, door, change tray, you name it, it's there. I found it in all those places," Fuller said.
Fuller said 90 percent of the vehicles he's stolen came from him just scoping out the vehicle, finding the keys, and taking the vehicle.
Most importantly, Fuller said if he found a key to the car inside of it, it's not a felony. "It's called joyriding. It's a misdemeanor, and I could take that vehicle, having a key to the vehicle that belongs to that vehicle," he said. "It's less risk to me."
quicklist: 6title: There Might Be a Key Inside Your Car You Don't Know Abouttext: "Well, there are some vehicles that have valet keys... and a lot of people don't know that they have a valet key inside their vehicle," Fuller explained.
Valet keys usually can unlock the driver's side door and start the car, but can't unlock the trunk or the glove box. This key is normally used when someone else operates your vehicle, such as a valet parking attendant. For example, Fuller said the valet key might be found inside the owner's manual. In some BMW models, the valet key is usually in the car's tool kit in the trunk.
While most people don't know they have a valet key, car thieves do, and they use them to easily steal and drive away with a car.
quicklist: 7title: The Biggest Mistake You Could Make Is...text: Leaving the window open even one inch can be just what it takes for a car thief to easily steal your car.
Most people believe that they can leave a little air in the car with the windows opened just a crack, but that no one can get in to the vehicle.
To Fuller, a car with window cracked opened was an unlocked car.
"A window that has enough room for me to stick my fingers in, I can get out of its track by rocking it back and forth until I get it out of the track," Fuller explained.
"Then, I can pry the window out of the track enough to where I can get my arm down in there and unlock the vehicle."
Watch ABC News' "20/20" on Friday, Nov. 22 at 10 p.m. ET, to see what happens when we let Steve Fuller try to steal three cars from a parking garage.