How much to store, how to store it, and how to make water safe to drink.
How much
At least 1 gallon per person, per day.
Keep at least a 3-day supply; 2 weeks if you can.
Store extra for pets, nursing or pregnant mothers, anyone who is sick, and hot climates.
Storing it
Store-bought bottled water is simplest - check the date on the bottles.
If you fill your own containers, clean and sanitize them first, label them "drinking water" with the date, and replace the water every six months.
Keep water somewhere cool (about 50-70°F), out of sunlight and away from fuel or chemicals.
Making water safe
If you are told your water may be unsafe, use your stored water first. If you must treat water, boiling is the best way. If you cannot boil it, unscented household bleach works for most germs.