So the world just ended, but you're still hanging on. Here are the first steps you should take to keep your belly (reasonably) full.
The first thing you should do is assess your current resources. How much food do you already have readily available? By doing so you gain vital information regarding if/how soon you must move, and therefore if you can remain stationary from the get-go or if you have to go nomadic to find food.
Depending on where you are and your resources available, you would be better off eating certain foods as soon as you can. Foods that spoil quickly should usually be eaten first, while canned and packaged foods can be kept for extended periods of time.
I have heard that it is a good idea (and I would agree) to keep an MRE or similar self-contained ration in your car/house in case of an extreme emergency. The MRE (Meal, Ready to Eat) is the current US military field ration. It stays good for about three years and can be bought on the internet or at military surplus stores. They kind of have a reputation for tasting really bad, but I've eaten one and it was pretty good.
Keep one just in case you find yourself without food when disaster strikes. Don't rely on them exclusively, but only until you can find other sources of food. Once you're relatively stable, then you are going to have to venture out and find food. Depending on your environment, this might necessitate taking different actions. These will be discussed in later posts.