You don't know who holds the key. Deadbolts are a necessity and provide added security. After dark is best to pull your shades or curtains to prevent someone from looking in your windows. Shrubs and Bushes Try to keep shrubs cut back below your windows and around doors to prevent someone from hiding in these areas. Lighting Lighting is one of the best deterrents for warding off a would be robber.
Motion detectors are wonderful and provide adequate coverage.
Timers placed on various lamps throughout the home are also recommended in the event you are not home before dark or while vacationing. Ask if you can make a call for them. Also, don't hesitate to ask for I.D. from a police officer, sales representative, or service person. If you are not expecting a service person it is a good idea to contact the company to verify if the representative should be at your home. If you live in an apartment complex or house, elevators can sometimes lead to trouble.