The two schools of thought are storing food like freeze dried, dehydrated, or MRE type supplies, and having the ability to produce fresh food on a regular basis.
If you take the first method exclusively, you need to determine what length of time you expect your emergency to last, the number of people (and Calorie level) you need to support, and store an appropriate amount of long storage food. It's important to be used to eating such foods, and cycle through your inventory to keep it fresh, and make your body adjust to these food types.
The second method assumes you have the ability to produce new food on an ongoing basis. This would work in the event of a distribution emergency (EMP or financial meltdown), but maybe not a personal flood/fire type emergency where your ability to produce is affected. A garden is common, and necessary in my estimation, as well as chickens, goats or a cow, fish, pigs, rabbits, or combination.
Ideally you will take a combination approach, as a bad frost, or hail storm could take out your crop, and you would need to fall back on storage until production gets online. A greenhouse is a common way to extend the growing season, and limit external influences.
Answers to raising chickens
How to Breed Rabbits for Meat, Profit and Fun.
Raising Goats Guide eBook
Organic Vegetable Gardening