Do not panic. Should an event occur chances are you will have advance notification and following a few basic steps will ensure a greater chance of survival. Below you will find a list of short term survival needs. Don't worry I will help you learn how to replenish this supply.
Water- Always keep a few gallons of water on hand. Keep some in your car and in your house. The more the better.
Food- Keep a small supply of canned and non perishable dry goods on hand. IE Canned beans, dry beans, dried fruit, rice, dry milk, powdered eggs. Most of these can be purchased at your local grocery store or camping supply store.
Battery Operated Radio and extra batteries. A small ham radio will not hurt either.
Flashlight candles and again extra batteries and bulbs.
Basic first aid kit. Should have bandaids, first aid ointment, rubbing alcohol, lighter or matches kept in a water proof ziploc bag,Peroxide, Iodine, tweezers, multiuse tool, rubber gloves, orajel, aloe vera aftersun gel with lidocaine, ace bandaid, popsicle sticks, guaze and surgical tape, hand sanitizer.
Survival kit- Matches, Lighter, Good pocket knife and Swiss Army Knife, Nylon Cord, Trashbag, Protein powder, water bottle, quinine pills, hand sanitizer, small pair of bolt cutters.
Books- Very specific books. You need to invest in a good book that describes wild edible and medicinal plants for the area you are in and the areas you intend to be traveling through. Pictures in said book need to be high quality. Second book should be a wilderness survival guide. Again find one that has clear pictures descriptions and illustrations. VERY IMPORTANT: Read these books prior to any event and familiarize yourself with basic elements of these books.
Guns- This can be a difficult topic for those who are not comfortable with gun ownership. If you do not own a gun and can not feel comfortable with a gun at least get yourself a good Bow or Knife. If you own a gun make sure you can shoot it correctly and comfortably. Keep extra ammo on hand. Know the basics of your gun. I am not giving you cart blanch to pull a gun on other people here... Just saying you may need this to provide food for yourself and family.
Society- If it seems everyone has gone crazy try to avoid large cities. I have a feeling this will not be the case in many areas and in fact people will pool together and share resources.