In order to understand what categories might be used to organize best practices for reducing teen violence, we must look at the causes of that violence. Each type of cause might offer us a category for best practices.
One set of causes of teen violence appear to be connected to the circumstances in which the teens grow up. These are causes that actually occur before the teen years (in some cases before birth) but which have an impact on behavior during the teen years. This leads us to at least two categories of best practices. First, there are practices having to do with the physical health of children. These include things like prenatal programs for mothers in at-risk areas. Such programs can improve the nutrition practices of mothers and can help prevent exposure of their unborn children to toxins from drugs or alcohol. This reduces the level of physical factors that might lead to violence in the future. A second category of best practices are social rather than physical. These are programs that aim to help parents of at-risk children in various ways that improve their children’s chances. Mothers’ mental health programs are one example. So are programs to help them with parenting skills.
A second set of causes have to do with teens’ attitudes and opportunities. This means that there are best practices that have to do with lessening teens’ propensity for violence. These include things like programs to promote more positive social interactions between peers. Programs could teach teens things like resisting peer pressure with respect to violence. They could teach teens about how to stay out of gangs.
Finally, some sociologists feel that access to guns is a major cause of serious teen violence. This leads to best practices having to do with guns. These are practices that are generally more connected to policing. There are strategies, for example, that focus on intensive pressure on at-risk teens by the police. The police can make clear to at-risk teens that they are being watched and that severe consequences will come with illegal possession or use of firearms.
Thus, there are a number of different categories of best practices for preventing teen violence, each connected to a different cause of that violence.
I don't think that there is one particular answer to this question. I would suggest that one potential avenue that could help to prevent criminal activity in teens would be to address the issue of gangs. Outreach programs in which community, local law enforcement, as well as schools and churches can be used as potential diversions for at- risk children who might be enticed into the gang culture and their affiliation. Gang violence is a major cause of criminal activity in teens, particularly in homicidal activity. In cities like Chicago, gang activity accounts for much in way of the homicide numbers being driven up so high. Infiltration of the gang activity through outreach programs can also help to forge a greater embrace of ways to stop the shootings. The "code of silence" that pervades the community is one in which "snitching" is frowned upon, helping to continue the alarming trend of crime and homicides. In Chicago, Mayor Emanuel has addressed this recently in the wake of the slaying of Hadiya Pendleton: "If anybody has any information, you are not a snitch, you're a citizen. You're a good citizen in good standing if you help." A way to potentially reduce criminal activity in teens would be to develop the outreach in which they are able to feel comfortable in refusing the lifestyle of gangs, or at least being able to feel a level of trust in being able to speak to the authorities about criminal activity in their neighborhoods. These could constitute as categories for the prevention of criminal activity in teens.