Here is the best simple overview on prepping. The first simple thing to do is build a closet of canned foods, dried rice and beans, and vitamins. http://preppednation.net

The decision on whether to stay put or head for the hills will be a complex one and made on a case by case basis. You don't want to easily give up the best shelter you have: your home. On the other hand, city life could become unlivable with no lights and no trash collection, vermin and disease could break out and marauders will be going house to house looking for food. One important thing will be communications. Start a CB radio club and test it on Saturday nights by saying howdy to your neighboring city slickers. Mutual support, trading supplies, and look-out duties will be key. Remember during the Rodney King riots in LA how the Korean shop owners banded together and took positions on the rooftops of their businesses, and faced down looting mobs. Iconic photo. That's who is going to make it. Well-armed, well-organized, communities. Someone on their own is just a target.

Ah yes, remember CB radios are only good as long as you can charge them. Shitloads of batteries will be a key commodity. After that learn to build a bicycle generator out of a motor and a converter to put out AC current.