Maybe not a popular opinion, but: Encourage your neighbors to call the police when things happen. Call them yourself, too.
I lived in a bad neighborhood for about 20 years, and have had family living in the "same" bad neighborhood (about 10 blocks away), and the difference in crime is night and day. The main difference from what I can tell, is that nobody on my street called the cops, ever. If I didn't call, the cops/fire department wouldn't show up.
For example, we had a mentally ill meth addict wandering the streets, breaking into vacant houses, vandalizing property, etc... One day, I find him starting a fire in some brush outside our house. My neighbor's way of dealing with this? Get out the hose and put the fire out. That's it.
I called the fire department, who alerted the authorities, who detained him.
Later that day while driving around, I saw half a dozen piles of ashes where he (I assume) had set fires before wandering off to start a new one. All within a 1-2 block radius.
I honestly think I was the only one who finally called the authorities on him, because everyone else in that neighborhood is so apathetic (or maybe so suspicious of the police) that they refuse to call 911.
He could have set a house on fire and killed a family. I'm speculating, but I imagine he wouldn't have even got the first fire started in a neighborhood that is vigilant and willing to call the cops.