First a side note.How prepared can anyone be? It'll be a sh*tshow no matter what.
I'm better prepared than 99 percent of the population, and I tend to doubt it will matter much.
That said, I think the key to such an event, if one is to have any chance of surviving it, is to make it past the first 45 days or so.
Here's my guess about what would happen (and it will vary by location):
For the first 48 hours, people will hunker down hoping that the power will come back on.
By the end of the first week, chaos will reign; might even start by the 3rd day. People will be panicked to find sources of clean water, and any kind of food. Some will figure out they can purify water by boiling it (if they can find fuel), and some by using chlorine.
By the end of the second week, most local fauna will be hunted out. Our local deer population, which herd numbers about 22, will be decimated. They're pretty tame (they walk through our yard all the time), so they'll be easy pickings. That may stave off some panic, but people still will be very distraught. We might see a significant number of deaths by then, from dying of thirst, violence, and for those who depend on electricity to stay alive, a lack of sufficient services to sustain them. How much thirst will be a problem depends on the local sources of water. Upper midwest? Maybe ok. Around the great lakes? Also maybe OK. Desert southwest of the US? Problem.
Those dead people will be an issue. Most local places will likely figure out a location to take the dead bodies, but burying them will obviously be a problem. Hauling bodies will be an issue with few or no working vehicles.
By the end of the third week, we'll see a lot of people gone. We'll also see the beginnings of people on psychotropic drugs whose medications are running out, and there's no resupply. Paranoia, depression, crazy violence--these are all likely consequences, especially with the enormous stress from just trying to survive.
One would also, in many places, expect roving gangs trying to "live off the land" as they go through houses looking for food and water. Many of the deaths noted above will come from gunshot wounds and bow and arrow.
By the end of 30 days, death will be rampant. People will be eating whatever they can get their hands on. It depends on when such an event would happen--if in the early fall, then local crops could mitigate hunger for a time. Apples, berries, sweet corn--these would help. If in the dead of winter, there would be severe problems heating places up north. People would crowd together in dwellings just to share heat.
By the end of 45 days, there will be enough death that many of the threats from the first 30 days will no longer exist. In some cases, people may band together to provide both security and shared sustenance. Those with mechanisms to purify water will be much ahead of others.
And after that? New meaning will be given to "living off the land." It'll truly be survivalism. Those with much food stored will be way ahead, provided they can keep it and defend against others who will do anything in desperation to get it.
No internet. No electricity. No cell service. No natural gas. No deliveries of fuel oil. No furnaces work, because no electricity.
Next to a widespread nuclear war, in the pantheon of disasters this is the worst scenario I can imagine.
My son in law is a super trained car mechanic with an engineering background. He said that modern cars are super insulated against electromagnetic interference because of all of the computers in them so he believes that most cars will still run after a CME or EMP.
In Rural areas like where I live power outages of 1-6 days are not uncommon. Most people have generators that can run the wells and 3-10 days worth of gasoline. When the grid goes down normal life continues with most people going into work and many of the stores and businesses also have generators. Most homes have propane for cooking and hot water along with a bit of extra food.
With most cars able to run I suspect that the primary problem with a long term grid down event would be people from urban areas "running to the hills" and overwhelming the more rural areas.