Be certain your wires are hidden, if you have installed a security system in your home. Many intruders bypass a security system by cutting the wires. Don't let this happen; bury or hide the wires. Your system will be far more effective this way.
If someone comes to your door selling items or claims to want to check something out for repairs, ask them to slide you their ID through the mailbox or under the door. Some robbers will come into your home to case it out, and their sales pitch can sound spot on.