Given everything I've seen, the most likely scenario for the average citizen is that food prices will increase and variety will decrease for a while. I don't see an all out famine being allowed to occur but I also don't see how things won't be at least temporarily interrupted and thrown out of rhythm. Especially given the amount of international trade going on these days. So my advice is have some raw calories on hand first and foremost, rice, beans, dried or canned anything that keeps well for a long time. Make sure you also have a few bottles of a good QUALITY multivitamin with a far off pull date. If you're taking one of those every few days and getting a bare minimum of calories that could be the difference in a worst case scenario. That said I'm not expecting one, so once I prepare for the worst I move onto getting extras of all the first world comforts that might not be so easy to find in a moderate food crisis. Psychologically, having some of the little treats you like when they're hard to find can go a long way. There's a lot of different levels and angles to look at it all from.