It means ethnography rather than law enforcement. Harm reduction means outreach, taking social and health services to people on their own turf and on their own terms. It also means making the system more accessible and more user-friendly rather than defining the user as an enemy be defeated. It involves real drug education for young people about the benefits as well as the harm of drug use, education about how to use drugs intelligently. It means making safer drugs for future users rather than trying to keep them from using drugs at all.
Harm reduction means making less harmful options available.
If we make coca tea available, most people will choose that form of cocaine over more harmful forms like crack, as a matter of simple survival. People can make choices that reduce the harm to themselves and to society. It means helping the drunk or the junkie get services, rather than throwing the drunk or junkie or crackhead or speed freak in jail. Harm reduction means reducing the harm to police, too. It means that if a cop goes to pat someone down and gets stuck with a needle, the chances are much less that the cop will become HIV infected if the needle has been cleaned with bleach or has been obtained from a needle exchange.