After the initial FALL
After things go belly up, people will be extremely nervous about going out. They'll have to, as it will be certain that most people didn't plan, and hence they'll be hungry, thirsty, scared, and in need of answers. Remarkably, that hunger for information will be a stronger compelling force than the other three.
We are only strong together. The earliest societies figured that out. A single family poses no threat to outside invaders. NONE.
What can you do to make the neighborhood safe again?
First, you've got to get people trusting again. It's dangerous to go door-to-door, but someone must do this.
Approach houses cautiously, calling out with your hands held at your sides and open clearly demonstrating a lack of threat. Have someone stand behind you, but far enough away that that person has some distance from the neighbor you are approaching. They should be armed, but not you. This requires bravery and diplomatic finesse.
Say, "I am not seeking anything except to talk. I don't want anything. I am only checking to see if YOU need help." If they don't immediately shoot you or threaten you, then continue. "I need you and you need me. We cannot make it alone in this neighborhood." If you have a little food that you can spare, it will go a long way to beginning the parlay.
Always keep your front facing the person you are talking to. Others are watching you from their windows, either within that person's home, or from neighboring windows. They are all scared, and may react in bizarre ways. You must stay vigilant. This is not an activity for wimps.
Try to organize by going to the most rational and well-liked people first. Popularity will help.
The first order of business is a neighborhood watch. This helps everyone. Try to get volunteers to check on the elderly or any children who might be alone. A parent who is medically fragile could have died, leaving children helpless.
If the trust level is high enough, some of the stronger men may volunteer to help set up a watch. Be judicious in setting it up as some people are power hungry and trigger happy. If you can, block the roads with cars to minimize outsiders coming in. It will help minimally. The watch can man stations to control entrances. No one will like it, but it will help.
Identify who in the neighborhood has a criminal record. Watch carefully for rumors. In the absence of knowledge, rumors spin out of control. Despite that, you must know where any risks might come from.
If the water is not working, it will be the first order of business. It takes a lot of strong people to gather water and transport it to where it is most needed. Organizing a crew to do this will help everyone out. Someone will have something to transport it like containers, wheelbarrows or garden carts, or ideas about filtration.
Set up a market day. Find a central location. Have people bring things they don't need as much, and wish to trade. It's an opportunity for people to start trusting again.
Someone in the neighborhood may be good with children or be a teacher either past or present. Try to organize something akin to a school.
Someone in the neighborhood may know something about medicine. Organizing all the medical supplies in one location will allow for a quantum leap in saving lives.
Spirituality will help as will tolerance in equal measure. People align themselves on a long continuum on the priority for these things. Do not impose your beliefs. Your actions are far more important than your words.