In addition to being a quality human in these ways, I'd recommend googling "tactical urbanism." That means: do quick, low-cost interventions in your neighbourhood, like painting a mural on the street, building flower boxes, or creating a pocket park. (Should probably get permission, but for some things, just do it). This all helps attract people to the street and builds a sense of ownership, which encourages folks to make more improvements, creating self-reinforcing momentum. All this reduces local crime, both because of eyes-on-the-street and because it creates a feeling that people are paying attention and care about the place.
If you have abandoned commercial spaces, put art up in the empty windows to reduce the feeling that a place has been abandoned. If your streets feel dangerous because of traffic, work with local leaders to get approval for making low-cost changes to make it safer. For example, you can create sidewalk bumpouts using simple flower boxes. Talk to local lenders about what they can do to help local businesses get off the ground.
Be warned that if all this is successful, it risks leading to a big jump in housing prices, i.e., gentrification. Keep in mind that "gentrification" also tends to make local residents wealthier — it's not as simple as the usual picture in which locals are simply pushed out. However, it is important to start thinking now about solutions, because this will lead to some push-back. Ideally, the city or nonprofits should buy land now while property values are cheap to create housing trusts for low-income residents. This will always be a tough issue though.
There is a lot of small actions you can take locally to shift the momentum of your community. Lots of people have done it — you can do it.
Source: I'm an urban planner.