The "broken windows" policy. Try to clear every crime and punish the offenders for "minor" offenses before they escalate to doing serious crimes. If the minor punishment for minor crimes doesn't deter them, at least the repeat offender record can minimize the number of victims before they are eventually off the streets. We got burglarized many years ago, the police came out, gave me a slip of paper and a case number "for insurance purposes". When I pointed out a fat juicy fingerprint on the glass she shrugged her shoulders and left. If they at least lifted the print they'd have the perp's bad history when caught for something else so they couldn't play the "first time offense" plea.