Verify the identity of any repairmen. Use the telephone number listed in the phone book, not on their identification. If someone comes to your door asking to use the telephone, make the call yourself. Don't invite them in. Don't hide a spare key under the door mat or under a flower pot.
Thieves know all the good hiding places.
Plant thorny bushes under all windows. Invest in motion sensor lights and a good security system. Always double check doors at night and lock all windows. Be sure your garage door can be secured. Do not leave it open when you are away, an empty garage broadcasts your absence.