Should you spend your money on a home security system? A look inside a burglar's mind might help you decide.

1. Of course I look familiar. I was here just last week cleaning your carpets, painting your shutters, or delivering your new refrigerator.

2. Hey, thanks for letting me use the bathroom when I was working in your yard last week. While I was in there, I unlatched the back window to make my return a little easier.

3. Love those flowers. That tells me you have taste … and taste means there are nice things inside. Those yard toys your kids leave out always make me wonder what type of gaming system they have.

4. Yes, I really do look for newspapers piled up on the driveway. And I might leave a pizza flyer in your front door to see how long it takes you to remove it.

5. If it snows while you’re out of town, get a neighbor to create car and foot tracks into the house. Virgin drifts in the driveway are a dead giveaway.

6. If decorative glass is part of your front entrance, don’t let your alarm company install the control pad where I can see if it’s set. That makes it too easy.

7. A good security company alarms the window over the sink. And the windows on the second floor, which often access the master bedroom—and your jewelry. It’s not a bad idea to put motion detectors up there too.

8. It’s raining, you’re fumbling with your umbrella, and you forget to lock your door—understandable. But understand this: I don’t take a day off because of bad weather.

9. I always knock first. If you answer, I’ll ask for directions somewhere or offer to clean your gutters. (Don’t take me up on it.)

10. Do you really think I won’t look in your sock drawer? I always check dresser drawers, the bedside table, and the medicine cabinet.

11. Here's a helpful hint: I almost never go into kids' rooms.

12. You're right: I won’t have enough time to break into that safe where you keep your valuables. But if it's not bolted down, I'll take it with me.

13. A loud TV or radio can be a better deterrent than the best alarm system. If you’re reluctant to leave your TV on while you’re out of town, you can buy a $35 device that works on a timer and simulates the flickering glow of a real television. (Find it at faketv.com.)