Post-collapse will be a gang war over containerized food, water, and supplies, until you and others can establish enough agriculture to realistically feed your people. This could take a few years.
If you have the good luck to be braving the apocalypse where you’ve already been living, doing your research can change everything for you when the shit hits the fan (SHTF).
You have to know where every convenience store, grocery store, food bank, and pharmacy near you are located. If you really want to be solid, you need to do a deeper layer of research and find out where any warehouses containing food are. That is harder to figure out; unlike the locations of storefronts, it’s not necessarily public information. If you can’t get this data beforehand, upon the collapse you need to get a vehicle or at least a bike, and scout out every single procurement spot in the area, making a map.
To dominate at a procurement spot enough to harvest from it, you’ll need a gang, which I’ve discussed at length elsewhere.
Beyond that, choosing which procurement spots you utilize, in which order, involves strategic planning. Like in Starcraft, you will probably deplete the resources near you the fastest. This may make some sense in the short term. The closest spots are the ones you can establish dominance over most easily, and transport goods from most easily. But that means as time goes on, you leave yourself in a lurch, and you are forced to expand. If you first deplete resources far or a medium distance from you, it leaves full stores close to you in the mid-long term. Medium distance locations, as much as you can handle, are probably the right balance realistically. They balance transport and risk issues with proximity. But there may be an advantage to raiding procurement locations which are far from you, since no one expects you to go there, and hostile forces are less likely to succeed in tracking you back to your home base.
Again like in Starcraft, time is ticking. The stores of the world are not just sitting there unused. Everyone has the same idea. You need to be expansionist and haul all the goods you possibly can, from as many spots as you can find, as early on as possible as you can manage, because they will all be rapidly dwindling as other people grab them up.
Acquiring vehicles early on tremendously expands your radius of possible harvesting, potentially critical for getting in on as many spots as you can before other people steal the bacon.
Approaching each procurement spot becomes a time for the use of military tactics and maneuvers. It could be guarded by a gang, guarded by one or two people with guns, in use by others who are unarmed, or you could get lucky and find it empty. It might be a good idea to arrive from unexpected directions like the back of the store, or send part of your gang from a different direction than your main group as a fake-out to keep any potential guards distracted and off-balance.
You may consider seizing a procurement spot entirely and turning it into your shelter/settlement, but this invites contention as everyone and their brother takes turns visiting the place in hopes of finding easy pickings. However it does save you the need to transport the stuff.
Including some agricultural supplies like seeds and farming manuals in your prep storage may assist the eventual transition to growing food instead of eating spam out of tin cans for years. As people start farming, die out, or restore the infrastructure, the ferocity of competition over procurement spots will fade. If you are still living out of containerized food, that’s good, and it also helps you in your search for any other supplies or appliances you may start to take interest in once your immediate food & survival needs are less of a threat.