The easiest way to build up your food storage is simply buying a bit more of the canned and long term storage foods you usually buy.. For instance instead of buying the normal 10 cans of soup your family eats each month buy 20 cans.. so you have 10 for storage..
Remember to rotate your stock and only store foods your family actually eats.. Having 100 lbs of wheat that your family won't eat is no more effective than having none..
I have found that using a vaccuum sealing system in conjunction with canning jars makes storing dried goods (cereal, flour, bisquick, etc.) easier... I buy in bulk then divide seal and place the bags into canning jars (no heat sealing required) This allows me to store the item for much longer with the vaccuum seal keeping the food fresh and the jar keeping out pests who can and will gnaw through a bag.. It also allows for easier storage in my gravity feed rolling racks while automatically rotate my stock..
Auto rotation... YES!!! a no brainer... Feed new product into the top and use from the bottom... Remember to date everything when you add it and it couldn't be easier.. (I use self stick labels "Address labels are great" on the canning jars write with a peramanent marker "I have a few on strings hanging from my racks so I can always find them"... Write directly on metal cans... Simply the date purchased will do...
I built my storage simply buying an extra weeks worth of food every paycheck.. It didn't take long to build up a pretty substancial storage..
Also think about storing seeds (Carrots, tomatoes, etc. etc. ) Should a crisis lead to the use of your storage having seeds will give you a way of growing food should the crisis be a really long one...
Also look into compiling a mobile 72 hour emergency kit... (3 days worth of food, water, some clothing, some cash, and other items in a portable container/containers..) Should you need to evacuate in an emergency(fire, flood, other natural disaster) You are ready to roll at a moments notice...
I store my 72 hour kit in a rolling rubbermaid trashcan with the lid inverted and a disk of wood on top and a table cloth it sits in my livingroom disguised as a side table with a lamp on top.. (Date the items inside and rotate them)..
Addition:
To Tonya in TX... Yes I have about 100 gallons of water in 5 gallon containers. (Crystal Bottles Water) I rotate them as well... Also for water there is roughly 3-5 gallons of clean water in the tank portion of all standard toilets.. As long as there is no in tank bleach or other cleaning product the water is fresh... (Please note I say tank not bowl) I also fill both bathtubs in my house when a storm is coming in that's another 150-200 gallons of water to use for cleaning etc. (not good for consuming)....
Everyone should take a look inside their toilet tank occassionally to make sure all parts are clean and rust free (it costs less than $15.00 to buy all new bits for inside most toilet tanks.. With clean properly maintained inside bits the water is there and ready to go in an emergency) Be sure to either turn off the intake valve or brace the mechanism before removing water as you don't want potentially contaminated water entering when the level drops..
Also your hot water heater is a great source of clean water.. Turn off the heating mechanism, turn off the intake valve and drain from the lower emergency drain valve.. Another 50-75 gallons of clean water....