Burglars know the best places to find keys hidden outside your home. Instead, give an extra key to a trusted neighbor. If your doors don't fit tightly in their frames, install weather stripping around them. Install a peephole or wide-angle viewer in all entry doors so you can see who is outside without opening the door. Your landlord generally will not be responsible for your possessions.
Thieves hate bright lights.
Install outside lights and keep them on at night. Buy radios, tape and CD players that can be removed and locked in the trunk. Remove valuable property from your car whenever possible. The thief will look for an easier target. Park in busy, well-lighted areas.