This is a bit of general advice I gleaned from living through the utter anarchy that followed the earthquake, in no particular order. I write this in the hopes that it helps someone someday.
Get to know your neighbors. You may have an arsenal, or a stockpile of food, or whatever else you think you need, but you can never be completely self-sufficient. Self-defense (neighborhood defense) is a good example of this. A lone guy with a handgun is less threating to a mob than two dozen angry homeowners with baseball bats.
Get to know your neighbors. I insist here. One may be a doctor. Another a mechanic. One may be able to jury-rig an electric pump for a well when the electricity is gone but there are car batteries to be had. One may know how to cook great food with whatever half-putrefact crap is left to eat after 10 days.
Keep spare water at home. They say a gallon a day per person, but if you stop bathing (which we did) you can get by on less. We had virtually no water, though, and the municipal water was cut off for two weeks in our area (in others, they still don't have any), which was a big problem. My wife and I spent hours a day scouring town for one of the very scarce water trucks that were around.
Get to know your neighbors. You may have tons of beans but no water. They may have nothing to eat, but they may have a grill. Another may have charcoal. Yet another may have water. If you get together, you all eat nutrituiously. If you don't, you all go hungry. If there's one thing the survivalist literature I've read gets wrong, it's that you can make it completely on your own. That's mostly fantasy. You need to join together with neighbors for many things -- from everything I mentioned above to self-defense.
Keep alternative sources of fuel at home. Our gas was cut off for nearly three weeks, gas cylinders couldn't be had anywhere, and all the stores were closed for more than 10 days, so we couldn't buy even charcoal. We used what charcoal we could gather from people's barbecuing leftovers, and then we went around the city gathering firewood. Shipping pallets work great for this. Remember, you also need to boil all your water in such a situation, so that means lots of fuel.
A battery powered radio is vital. Rumors spread like wildfire on a sea of gasoline in catastrophes, and they can cause great harm. You need solid information -- on where water can be found, where there are riots and active looting, what parts of what hospitals didn't collapse, etc. In our case, I jury rigged a really long wire to the antenna of a radio to be able to get long distance transmissions while the local station was down.
People will panic. People will turn into hoarding bastards, even if it means stuff everyone else could eat rots. People will have no idea what to do. I learned in this experience that most people are sheep, and many can turn into wolves if allowed to, if only due to the effects of sleep deprivation, terror, uncertainty, malnutrition, etc. If you've got even a bit of leadership in you, lead!! People need that. Assign them tasks. Keep them busy. Organize patrols. Have an official radio listener. In these situations, it's not "If I don't
lead, someone else will" -- it's actually "If I don't lead, no one at all will".
Get to know your neighbors. One of ours, who I only met after the earthquake, works for a utility company, and his small connections got our electricity back on earlier than in neighboring areas.
If you lead, you need people to follow you. Most will, simply because it's comforting. In all other cases, just work harder than everyone else, and then even the stragglers will respect and follow you.