I've seem lots of people invest in alarm systems, guns, vaults etc. and totally skip the obvious things. Mind what you sit out on the street to be picked up. You can learn a lot about someone by their trash. Example, sitting the box your 82" plasma came out of on the curb, not a good idea. Don't advertise what you have. My Mom taught us this growing up. Break big boxes down into smaller pieces and put it out in a bag with trash or recycle.
People driving or walking past your house can see what you have in many ways. Open windows and doors, sure the breeze is nice on a cool evening but people can see more than you think. Don't be fooled by words like "gated", "master planned", "community", "guard" etc. Often times the people you need to worry about live within the same gates that you do.