In this day and age it's probably impossible to be completely self-sufficient but it's nice to aspire to a greater level of sufficiency then one is currently at.
Back in the cold, frozen North we had a 1/5 acre plot that we grew a ton of produce on. We were just starting to plant fruit trees when we decided to move. Even then on that little city lot we tried to lessen our impact on the world, become more frugal and increase our self sufficiency.
I have a list of things that I'd like to implement on this property.
Grey water catchment system: This is something you have to check with your municipality before installing. You don't want to spend money here only to find out after the fact that it's illegal where you live.
Solar Panels: The gold standard of self-sufficiency. It's pricey but we're hearing a lot about a new improved and cheaper panel coming soon to the market.
Wind Power: There is a fair bit of wind here so why not harness it for energy production?
Rain Barrels: With lots of thirsty animals around, I'd like to rely on something other than the well to water them with. Strategically placed barrels will make dragging around a giant hose a thing of the past.
Food Production: We've already started on this with the chickens and pig. The goats should be ready to milk soon taking care of our dairy needs. Gardening will of course be the biggest contributor. In addition to the regular fruit and vegetables, I'm going to attempt edamame, chickpeas and oats this year.
Food Storage and Preservation: I'm hoping Limey will have time to set up a cold room in the basement before harvest in the fall. I've been dreaming about solar dehydrators, pressure canners and smokers.
Here's some links to more info;
The National Center for Home Food Preservation
Ball Canning Recipes
Solar, Water, Biofuels...