No one knows preparedness like the Marines. They face things in combat that other mere mortals cannot imagine or comprehend. Because of this, they are the authority on preparedness for when (not if) the SHTF. There shared wisdom is available for download via their website, and you should consider printing yourself a copy of The Marine Special Operatons Training Guide for when (not if) the lights go out. Certain things are priceless in a survival situation, and this guide is very much one of those things.
One notable piece of information is regarding socks. Ever heard of trench foot? It is a nasty little condition that comes from having feet that are constantly wet and subjected to unsanitary conditions. Your feet become necrotic, gangrenous, and may require amputation. The Marines suggest wearing appropriate socks that provide padding and wick moisture to avoid things such as trench foot.
Also important is going over or around obstacles without stepping directly on them. This is valid because it is not always obvious where there is danger. That harmless looking log you were about to step on probably would have rolled, causing you to fall and break a leg and bust your head open. When you are laying there, bleeding and in pain, you will be wishing someone had shared information with you that could have prevented your injuries. The Marines say you should not step on that log, and you ought to listen.
Physical fitness is key. You cannot realistically sit around eating Twinkies and expect to be able to outrun a horde of hungry zombies. Sure, you can probably escape a few of the shambling sort, but the ones that can run are mighty fast. Zombies also don't get winded, but you sure will. The Marines mentioned that you should be following an exercise regime and it looks like they are probably right. They also discus several exercises that can be performed practically anywhere with little to no equipment to purchase.
This guide is meant to prepare incoming MARSOC candidates for the rigors that is a modern special operations force. Bottom line is, if you can handle the physical guidelines of this manual, you might be prepared enough to handle yourself in a survival situation.
Preparedness is not exclusively about stocking your underground bunker with non-perishables and batteries. There are many other tasks you will need to attend to if you are to survive. At some point you are going to have to stock your body, too, and that means starting well ahead of time by eating right and working out. Remember that the strong survive, and know that being strong will help you survive. Being weak will not only get you killed, but might also get you eaten.
You don't want to go out with some zombie taking a bite out of you and declaring that you taste like Twinkie.