 Don't open your door to strangers. That may sound basic, but many people are fooled by the high visibility vest and the box they're carrying. Think about it this way. What good does it do to install a security system, a high security steel door with two deadbolts, a chain and a lock, only to open the door to anyone who knocks on it? Before opening the door, first look out the window for a marked delivery truck. If you don't see one, then talk to them through the door to get further information.