If you wear corrective lenses, keep a back-up pair of glasses and/or lots of extra contacts.
If you require prescription medication, maintain a back-up supply. More than you think you'll ever need.
Keep a substantial stockpile of emergency food, water, first aid and camping supplies on hand.
Always keep your gas tank full and your vehicle well maintained.
Know some basic self defense techniques and be comfortable using firearms.
Know how to grow a garden, forage, hunt and fish.
Have all your important phone numbers and addresses written down on a piece of paper.
Have a plan on where to meet your loved ones if you are all away from the house and the transportation grid goes down.
Know where all your important documents / passports / cash etc. are located in the house and ready to grab at a moments notice.
Have an up to date (and detailed) map book in your collection (not just for your local area, but your entire State/Province/Region) - Back roads atlases are the best.
If you live in a large urban area, have a plan on how to get out quickly. Know where all the bridges and bottlenecks are, and how to get around them if need be.
Most of all, try not to worry because I'm sure everything will be just fine.