Those two items in the thread title are pretty broad, but in a prolonged grid-down situation, keeping your food sources from being pillaged and keeping your possessions in your homestead from being stolen are pretty big deals.
http://secretsofurbansurvival.com/398/h ... invasions/
Personally, I'm intrigued by the possibilities in growing root vegetables such as carrots, turnips and parsnips and hope to try my hand at sweet potatoes. Pillagers can't take what they can't find.
Here's another link:
http://www.survivalblog.com/2010/09/let ... k_and.html