The secret for security is to delay them beyond the point that it's worth their effort, or expose them to the point they are uncomfortable taking the risk. Nothing is going to stop a dedicated thief, but most are just out for a quick score that they can sell for drugs. A good chain and high quality lock go a long ways in deterring them, but never underestimate the creativity of a crack head. Night lights are their worse enemy, as are dogs and alarms. Motion sensors are alright, but not overly reliable. A light on all night long is one of the best ways to keep thieves away.
Eddie