Be prepared for what? For  anything that could potentially harm you or your family. Let me ask you this,
how long could your family last without a restaurant or grocery store?
If your answer was not 3 months or more,you need to do a little stocking up. Here is the thing,
if nothing ever happens it's food and water and you eat it.....
If something does happen you will be glad you protected your loved ones.

Water

One gallon of water per person per day, for drinking and sanitation.
Children, nursing mothers, and sick people may need more water.
If you live in a warm weather climate more water may be necessary.
Store water tightly in clean plastic containers such as soft drink bottles.
Keep at least a three-day supply of water per person.

Food

Store at least a three-day supply of non-perishable food.
Select foods that require no refrigeration, preparation or cooking and little or no water.
Pack a manual can opener and eating utensils.
Avoid salty foods, as they will make you thirsty.
Choose foods your family will eat.
Ready-to-eat canned meats, fruits and vegetables
Protein or fruit bars
Dry cereal or granola
Peanut butter
Dried fruit
Nuts
Crackers
Canned juices
Non-perishable pasteurized milk
High energy foods
Vitamins
Food for infants
Comfort/stress foods
Medical supplies
Things you should have:
Two pairs of Latex, or other sterile gloves (if you are allergic to Latex).
Sterile dressings to stop bleeding.
Cleansing agent/soap and antibiotic towelettes to disinfect.
Antibiotic ointment to prevent infection.
Burn ointment to prevent infection.
Adhesive bandages in a variety of sizes.
Eye wash solution to flush the eyes or as general decontaminant.
Thermometer (Read more: Biological Threat)
Prescription medications you take every day such as insulin, heart medicine and asthma inhalers.
You should periodically rotate medicines to account for expiration dates.
Prescribed medical supplies such as glucose and blood pressure monitoring equipment and supplies.

Things That may be good to have

Cell phone with charger
Scissors
Tweezers
Tube of petroleum jelly or other lubricant
Non-prescription drugs:
Aspirin or nonaspirin pain reliever
Anti-diarrhea medication
Antacid (for upset stomach)
Laxative
Some potential emergencies could send tiny microscopic "junk" into the air. For example flooding could create airborne mold which could make you sick and an explosion may release very fine debris that can cause lung damage. A biological terrorist attack may release germs that can make you sick if inhaled or absorbed through open cuts. Many of these agents can only hurt you if they get into your body, so think about creating a barrier between yourself and any contamination.
Nose and Mouth Protection
Face masks or dense-weave cotton material, that snugly covers your nose and mouth and is specifically fit for each member of the family. Do whatever you can to make the best fit possible for children.
Be prepared to improvise with what you have on hand to protect your nose, mouth, eyes and cuts in your skin. Anything that fits snugly over your nose and mouth, including any dense-weave cotton material, can help filter contaminants in an emergency. It is very important that most of the air you breathe comes through the mask or cloth, not around it.
Do whatever you can to make the best fit possible for children. There are also a variety of face masks readily available in hardware stores that are rated based on how small a particle they can filter in an industrial setting.
Given the different types of emergencies that could occur, there is not one solution for creating a barrier between yourself and any contamination in the air. Simple cloth face masks can filter some of the airborne particulates or germs you could inhale, but will probably not protect you from chemical gases. Still, something over your nose and mouth in an emergency is better than nothing. Limiting how much foreign matter is inhaled may impact whether or not you get sick or develop disease.
Other Barriers That are easy to make
Heavyweight plastic garbage bags or plastic sheeting
Duct tape
Scissors
There are circumstances when staying put and creating a barrier between yourself and potentially contaminated air outside, a process known as "shelter-in-place," is a matter of survival. You can use these things to tape up windows, doors and air vents if you need to seal off a room from outside contamination. Consider precutting and labeling these materials. Anything you can do in advance will save time when it counts.
Use available information to assess the situation. If you see large amounts of debris in the air, or if local authorities say the air is badly contaminated, you can use these things to tape up windows, doors and air vents if you need to seal off a room. Quick Check list!
Water, one gallon of water per person per day for at least three days, for drinking and sanitation
Food, at least a three-day supply of non-perishable food
Battery-powered or hand crank radio and a NOAA Weather Radio with tone alert and extra batteries for both
Flashlight and extra batteries
First aid kit
Whistle to signal for help
Dust mask, to help filter contaminated air and plastic sheeting and duct tape to shelter-in-place
Moist towelettes, garbage bags and plastic ties for personal sanitation
Wrench or pliers to turn off utilities
Can opener for food (if kit contains canned food)
Local maps
Cell phone with chargers, inverter or solar charger
Dryer lint in a baggie(great for starting fire)
Always have cash on hand in small bills, money in the bank is no good without power!