I'd like to take a post to point out something I see too often when folks start talking about disaster preparation. A lot of this conversation also applies to virtual situations, such as your common Dungeons & Dragons scenarios, so we've got a topic of broad applicability.
Put simply, a lot of such talk displays a dearth of clear thinking, and the tell is a lack of appreciation for focus upon the objective and the logistics required to make that happen. You get people too caught up in the guns and the survivalist fantasy, you've got people who don't think through the scenario and therefore don't prepare properly, and you have naive fools who don't think they need to do more than a token amount.
These fallacies exist because most of these people are urban or suburban people, life-long, and have never been in a situation where that fundamental scarcity exists. The power rarely, if ever, went out. The water was always on and potable. The markets had food and gas all the time. Government services worked, even in emergencies. Someone who never had to handle months out of contact with city life, or had to handle severe weather (such as hurricanes) regularly.
Nevermind the zombies; that's just an excuse to talk about this usefully in a social setting. The real thing to do is to talk about the most likely disaster scenarios, talk through the progress, identify likely outcomes, then come up with a plan and prepare to execute it.
That is exactly what a proper game of Dungeons & Dragons faces: logistical scarcity. Most games in this mode will have the player facing this issue, forcing trade-off considerations that shape decision-making, but always in light of the overall objective.
I'll return to this down the road with more specific follow-ups, but for now hold on to this: the ones who survive disasters are those that keep their head, focus on the objective, prepared accordingly, and follow the plan. Even when they have to adapt the plan, they still stick to it.