When you're preparing for or facing an urban survival situation, there is a rule that will help you prioritize. It's called the Survival Rule of Threes. It means, you can live:
* 3 minutes without AIR.
* 3 hours without SHELTER.
* 3 days without WATER.
* 3 weeks without FOOD.
* 3 months without HOPE.
Imagine you are stranded in the wilderness. It could be days or even weeks before you get home. If you're stomach is growing, you might go ahead and start collecting berries or setting animal traps. But what if the temperature drops and it starts raining? If the temperature is in the 40's or less, you will certainly get hypothermia. And before long, you'll be dehydrated. When that happens, you're head will hurt, nausea will make it difficult to eat, and you'll be too tired and weak to keep gathering food.
This can be avoided by following the Rule of 3's. The first thing you should do is build a shelter to protect yourself from the wind and rain. Next, find a source of clean water, or a find a way to purify the water you have (this might mean building a fire so you can boil the water in a container or with hot rocks). After all this, then you can start searching for food.
Of course, this rule applies more to wilderness survival situations, but it is also worth considering if you're going to survive in place in an urban disaster. You could call it the Urban Preparedness Rule of Threes:
When preparing for an emergency in the city, consider how these rules affect your preps. If the air is contaminated, you'll need a gas mask. You'll want to secure your home by reinforcing your doors and putting bars on your windows. If you really want to secure your shelter stock up on bullets and guns. Also, ask yourself how you're going to heat your home. Next, you should concentrate on water storage and water purification. After that, focus on food storage and everything you would need to cook that food. What other sources of food do you have? What do you need to grow it or hunt it? And finally, what about hope? Be sure to keep a Bible or whatever encouraging books, games or instruments you need to keep yourself sane. Happy preps!