Our Pet that Lives in the Refrigerator

Not that I would recommend keeping most pets in the refrigerator, but this one finds it the best environment to sleep in. When I take it out and feed it, it springs right awake, ready to jump out of its jar and just leaven something.
Our pet is a thriving yeast colony fabled to have once traveled the Oregon Trail. Because yeasts constantly multiply and regenerate, it is possible for the same strain of bacteria to survive hundreds of years - millions of generations - with proper care and feeding. Refrigerating or even dehydrating the starter just puts the little bugs to sleep, ready to spring back to life with the right amount of food and warmth.
It is possible to "catch" a wild starter using plain flour and water, which capture yeasts from the air. I tried that; it really isn't as easy as it sounds. I recommend, for beginners like myself, to start with a successful sourdough starter, whether it be from a friend, a mythical vendor like King Arthur, or a nonprofit operation like Carl Griffith. Carl's friends supply the Oregon Trail starter for the cost of two stamps. It arrives in powdered form, to be reactivated with flour and water, and has superior flavor and rising power than anything I've made myself.
I maintain my starter with 100% freshly ground whole hard white winter wheat at 100% hydration, which means I feed it equal weights flour and water. I store it in a mason jar, as pictured above, with a paper towel over the mouth secured with a rubber band.
A good starter should smell like bread baking. When fed, it should bubble up and double in size over several hours, then shrink again. There are as many different types and techniques of sourdough as there are people on earth. They're like snowflakes - no two loaves are alike. Slight changes in timing, temperatures and ingredients can produce an infinite variety of breads.
Sourdough Home was influential in teaching me the fundamentals of sourdough baking, as was The Fresh Loaf, but as they all say, there is really no substitute for old-fashioned hands-on experience.
My most recent sourdough experiment was with mini pizza rounds, which I prepared as follows:

Day 1:
Remove starter from the refrigerator and feed with one ounce each freshly ground flour and water.

Day 2:
Add twelve ounces each flour and water to a bowl containing four ounces of starter. Mix and allow to rest in a cool place (not the refrigerator) overnight.

Day 3:
Add three ounces freshly ground flour, two teaspoons sea salt, a tablespoon of olive oil, a tablespoon of Muscovado sugar or honey, and half a teaspoon of baking soda to the dough. It should feel the way a marshmallow looks while it toasts over the fire - puffy and soft - smooth, but not sticky. Knead it gently for a few minutes to ensure all of the ingredients are mixed; the dough really doesn't need that much attention. Over-kneading can cause the loaf to turn into a perfectly flat brick in the oven. Clean out the mixing bowl and oil the inside. Gather the dough into a floppy ball and return it to the oiled bowl, smooth side up. Cover and allow the dough to rise about two and a half hours or until doubled in size.
Divide the dough into sixteen equal pieces. Cut four squares of parchment paper the size of your baking stone if you have one. Place the baking stone in the oven and preheat it to 400 F and get an edgeless cookie sheet or pizza peel ready. Meanwhile, stretch and shape the little dough pieces into 4-6 inch rounds or rectangles. Place four on each piece of parchment and let them rise about an hour until slightly puffed. I didn't cover them. Slide the pizza peel (or cookie sheet) under one sheet of parchment and transfer it to the baking stone, and shut the oven for five minutes. Remove the baked rounds from the stone and replace with another batch of dough. Cook each for five minutes.
Now you have 16 pre-baked pizza shells, ready for toppings. After letting mine cool, I put them in a bag in the freezer. We had two of them the other night, topped with a little tomato paste, fresh spinach and mozzarella cheese, baked for 10 minutes at 350. They're perfect for a quick snack or a make-your-own pizza party, such as I used to have with English muffins when I was little.